Rescue workers searching for the dozens of people still missing in the wreckage of a highway bridge that collapsed into the Mississippi River Wednesday evening in Minneapolis were pulled from the water this afternoon because strong currents blocked their work.

Four people are confirmed dead in the collapse, officials said. That figure is likely to rise as bodies of the missing, who are estimated to be at least 20 but could be up to as many as 65, are recovered from vehicles that fell into the river from the Interstate 35W bridge. The span was filled with backed up rush-hour traffic when it gave way just after 6 p.m. Central time. Another 79 people were injured, officials said.

At least a dozen cars and trucks are in the river, officials said. Other vehicles remained on the pavement as it fell as much as 60 feet, and could be seen resting on the broken roadway as it lay on the river and its banks. Rescuers are working both on land and in the water, said Chief Tim Dolan of the Minneapolis Police Department.

Chief Dolan estimated that 20 to 30 people were missing in the bridge collapse. Mary Dooley, executive director of the Iowa Rivers chapter of the Red Cross, reported a higher number: 65 people still missing.

Richard Stanek, the Hennepin County sheriff, said that about 12 cars could be seen submerged in the river, and there are probably more out of sight below the surface.

Inspector Jeff Storms of the sheriff's department, is dive team leader for the search. He said debris in the water was causing "eddies," or swirling water, making it flow faster in some areas. Until the search was halted divers were going in two at a time, with two backup divers waiting in case of emergency, Inspector Storms said.

"We're regrouping for the safety of the divers," he said. "We're making sure we're taking this methodically."

At Hennepin County Medical Center in downtown Minneapolis, less than 2 miles from bridge, 15 victims were being treated today, with 5 of them in critical condition. One person treated at the hospital died, and the cause was reported as drowning; eight others were treated and released.

Forty more people were admitted last night to the University of Minnesota Medical Center-Fairview, of whom five had arrived by ambulance. Today, 16 of them were still being treated, and were reported in good or fair condition.

About 10 families gathered today at the Holiday Inn in Minneapolis, where officials had set up an assistance center for them. Most were awaiting information about missing relatives.

Chief Dolan described wrenching scenes during the rescue. One severely injured person who was talking to medical workers managed to say goodbye to family members before dying, he said.

Officials said that the recovery operation could take three to five days, and the bridge was being treated as a crime scene, though indications are that it collapsed .

Chief Jim Clack of the Minneapolis Fire Department said that most of the people rescued at the scene were reached within an hour of the collapse.

"This is a catastrophe of historic proportions for Minnesota," Gov. Tim Pawlenty said at a news conference late Wednesday evening.

On Thursday, the governor called for inspections to ensure that the state does not have another bridge of the same type, according to The Star Tribune. "The first thing we're going to do is make sure that we immediately inspect and check all bridges of this design and that fall into this category on the assessment scale."

Mr. Pawlenty said this morning that a federal government report on the bridge, making an assessment based on data provided by the state, "called for inspections, which we did, 2005-2006. Inspectors on the ground said yes, there is some fatigue in the bridge, but it doesn't rise to the level of being immediately replaced. In fact, it was slotted for replacement in about 2020."

He said later in the day that a final review of the bridge had been planned for September, after the current construction was completed, to determine if the bridge should be fixed or replaced.

The Minnesota Department of Transportation "did everything appropriate," said Mary E. Peters, secretary of the federal Department of Transportation, speaking to reporters at a press conference today. "But clearly we need to understand what happened here, Ms. Peters said, adding, "Bridges in America should not fall down."

"This is the first time in a very long time we have seen something like this happen," she said. "This is, to my knowledge, the second time we've seen a bridge of this magnitude go down without some specific reason, like a barge, since 1983." That was the year that a bridge collapsed along Interstate 95 in Connecticut.

Since then, federal transportation officials have incorporated improvements to their bridge inspection and rehabilitation program, Ms. Peters said.

Such changes were of little help to Melissa A. Hughes, 32, a warehouse manager, was headed southward over the bridge in a route that would have taken her past downtown Minneapolis.

"I was on the bridge when it happened," said Ms. Hughes. "I was driving home from work. It was bumper to bumper."

She was on a section of bridge that was remained above the land, but about three car lengths ahead of her, suddenly everything dropped from view.

"My sensation was seeing this thing suspended in air, you could tell the cars were not level, and I swear I saw a construction worker in the air," she said. And then she experienced what she described as a "a free fall feeling, like on an amusement ride."

"There was a huge smashing sound, and it was my back window getting blown in," she said.

She loosened her seatbelt, opened the door easily enough, but when she got out she found that her car had ended up at a 45-degree angle.

"And when I was on ground I could see it was a pickup truck had landed upside down on my car," Luckily, Ms. Hughes said, it was the bed section of the truck, which meant that it did not go past the back seat.

She and others around her gathered. "We all knew this bridge goes over the river and how fortunate we were to be on the section we were on, and not into the water," she said.

She has a stiff neck and back.

"It happened so fast," she said. "I knew I was safe on ground at 6:06 p.m., when I was calling my husband."

Mark Rosenker, chairman of the National Transportation Safety Board, said today that 19 inspectors would be arriving in Minneapolis to investigate the cause of the bridge's collapse, and they would review the engineering of the bridge, the highway and its materials, among other things. He estimated that the N.T.S.B. would complete its report in about a year.

President Bush, in a news conference today, expressed condolences for the victims and said "the federal government must respond and respond robustly to help the people there not only recover, but to make sure that lifeline of activity, that bridge, gets rebuilt as quickly as possible."

Ms. Peters announced that the Department of Transportation would send $5 million to Minneapolis to help to "give crews the support they need to begin restoring traffic flow, clearing debris, setting up detours, and making repairs."

The bridge was eight lanes wide, and carried the main north-south highway through Minneapolis. It was being repaired at the time it collapsed, and a witness told MSNBC that he had heard a jackhammer being used on the roadway just beforehand. Witnesses said the bridge, which was built in 1967, collapsed in three sections. One section of the bridge lay flat in the river, with some cars and trucks resting on the pavement.

The collapsed bridge, which was about 1,000 feet long, had been supported by a steel truss structure of somewhat unusual design. Repairs were being made to the bridge's concrete deck, guard rails and lights, state officials said.

The construction work was being done by Progressive Contractors Inc. of St. Michael, Minn. Tom Sloan, the company's vice president for bridges, told the television station KARE that 18 workers were on the bridge at the time of the collapse; by about 10 p.m., all but one of them had been accounted for.

Divers and rescue boats continued to search the river and the twisted wreckage of the bridge for survivors as darkness set in and rain began to fall. The Star Tribune said some people were seen floundering in the river, calling for help.

Leah R. Fulin, 16, of Minneapolis, had just crossed the bridge and was on the Washington Avenue exit ramp when it collapsed behind her.

"Most of the cars that were on the bridge went into the river," she said. "There was a whole bunch of smoke when concrete breaks like that. There were people screaming."

Janet Stately was returning from Duluth, Minn., and had decided to take an adjacent bridge to avoid traffic when the collapse occurred.

"I heard an awful noise and saw what looked to me like a piece of the freeway just going down flat," Ms. Stately said. Then she said she saw the road collapse into a V and cars rolling into the river. "I clearly recall horns honking. I was screaming. We were trying to call 911 on our cellphones."

A school bus could be seen on one section of the collapsed roadway, with its back door open. Red Cross officials said 60 children were taken off the bus by rescuers, and 10 of them had injuries that were treated at city hospitals. A short distance away from the bus, a tractor-trailer caught fire and burned.

"I saw a lot of crying," Courtney Johnson of the Red Cross told CNN. "Some of the older children were comforting the younger children." The children were 4 to 12 or 13 years in age, Ms. Johnson estimated.

The children were in a summer program, on the way to a swimming pool. Jeremy Hernandez, 20, a gym coordinator for the program, said he was sleeping on the bus when he heard a boom and thought the bus had been in an accident. Then the bus kept falling, it crashed, and then it fell again. When it stopped, the children on the bus were moaning and crying.

When the dust settled, "they all started screaming," said Mr. Hernandez. "They wanted their parents and wanted to hold on to all the staff, they didn't want to let go."

He opened the back door of the bus and passed children out to others. Berndt Toivonen, 51, of Minneapolis, told The Star Tribune he had been on his way home from a painting job when the bridge collapsed beneath his car.

"The bridge started to buckle," Mr. Toivonen said. "It went up and it came down. I thought I was going to die." He was uninjured, but he said people around him, some injured, were screaming in their cars. He told MSNBC that he helped some other people off the bridge.

Dr. Joseph Clinton, chief of emergency medicine at Hennepin County Medical Center, said six patients at the hospital had critical injuries and 22 had injuries that were not considered life threatening. There was one drowning fatality, Dr. Clinton said.

"This is a very busy bridge," said Senator Amy Klobuchar, Democrat of Minnesota, whose home is nearby. "It's really right in the heart of the city," Ms. Klobuchar told CNN. "Thousands of commuters use this bridge every day."

According to the Minnesota Department of Transportation, the flow on the eight lanes of I-35W crossing the river was supposed to be restricted beginning Tuesday night for the northbound lanes and at 8 last night, about two hours after the collapse, for the southbound lanes. The reason stated on the agency's Web site was "overlay work," which refers to roadway resurfacing.

The Minnesota Twins, who play home games in the Metrodome not far from the site of the bridge collapse, had a moment of silence before their game Wednesday night. Team officials decided to play Wednesday's game after public safety officials decided that sending 20,000 to 25,000 people back into traffic could hinder rescue efforts, the Twins' president, Dave St. Peter, told The Associated Press. Today's game against the Kansas City Royals has been postponed, along with a groundbreaking ceremony for a new baseball stadium, according to the Twins Web site.