MINNEAPOLIS – Divers checked submerged cars in the Mississippi River Thursday for victims still trapped beneath the twisted steel and concrete slabs of a collapsed bridge. As many as 30 people were reported missing as the rescue effort shifted to recovery.

Gov. Tim Pawlenty also ordered an immediate inspection of all bridges in the state with similar designs.

The official death count from Wednesday evening’s collapse stood at four, but Police Chief Tim Dolan said more bodies were in the water. Hospitals officials said 79 others were injured.

“We have a number of vehicles that are underneath big pieces of concrete, and we do know we have some people in those vehicles,” Dolan said, though he said he did not have a number. “We know we do have more casualties at the scene.”

The eight-lane Interstate 35W bridge, a major Minneapolis artery, was in the midst of repairs when the bridge buckled during the evening rush hour Wednesday. Dozens of cars plummeted more than 60 feet into the Mississippi River, some falling on top one of another. A school bus sat on the angled concrete.

The bridge was crowded with traffic, and a train had been passing beneath the roadway at the time it fell.

In the river, divers were checking for bodies and taking down license plate numbers for authorities to track down the vehicles’ owners. Getting the vehicles out was expected to take several days and involve moving around very large, heavy pieces of bridge.

Police estimate that 20 to 30 people were unaccounted for, though Dolan stressed that it was just an estimate.

At Hennepin County Medical Center, patients arrived in a steady stream after the collapse, some unconscious or moaning, some barely breathing, others with serious head and back injuries, Dr. William Heegaard said.

“There was blood everywhere,” he said.

Relatives who couldn’t find their loved ones at hospitals gathered in a hotel ballroom Thursday morning for any news, hoping for the best.

Ronald Engebretsen, 57, was searching for his wife, Sherry. His daughter last heard from her when she left work in downtown Minneapolis Wednesday. Her cell phone has picked up with voice mail ever since.

“We are left with the hope that there is a Jane Doe in a hospital somewhere that’s her,” Engebretsen said.

As many as 50 vehicles tumbled into the river when the bridge collapsed, leaving those who could escape to scramble to shore. Some survivors carried the injured up the riverbank, while emergency workers tended to others on the ground and some jumped into the water to look for survivors. Fire and black smoke rose from the wreckage.

“People who were pinned or partly crushed told emergency workers to say ‘hello’ or say ‘goodbye’ to their loved ones,” Dolan said.

The Homeland Security Department said the collapse did not appear to be terrorism-related, but the cause was still unknown.

The first step of the federal investigation will be to recover pieces of the bridge and reassemble them, kind of like a jigsaw puzzle, to try and determine what happened, NTSB Chairman Mark Rosenker said.

Investigators also want to review video of the collapse, and were setting up a phone number for witnesses to call with information.

“It is clearly much too early in the initial stages of this investigation to have any idea what happened,” Rosenker said.

As the divers worked their way around at least a dozen submerged vehicles, Transportation Secretary Mary Peters announced a $5 million grant to help pay for rerouting traffic patterns around the disaster site. Members of the state’s congressional delegation said up to $100 million could be available for repairs and recovery.

In 2005, the 40-year-old bridge had been rated as “structurally deficient” and possibly in need of replacement, according to a federal database. The span rated 50 on a scale of 100 for structural stability in that review, Peters said.

The U.S. Department of Transportation’s inspector general last year criticized the Federal Highway Administration’s oversight of interstate bridges, saying investigators found incorrect or outdated maximum weight limit calculations and weight limit postings in the National Bridge Inventory and in states’ bridge databases.

Incorrect load ratings could endanger bridges by allowing heavier vehicles to cross than should be allowed, the inspector general said. The audit didn’t identify any Minnesota bridges beyond noting that 3 percent of the state’s bridges were structurally deficient, placing it at the low end among states.

Pawlenty said that there was no indication from that and other reviews that the bridge should be shut down. Peters added that “none of those ratings indicated there was any kind of danger.”

This week, road crews had been working on the bridge’s joints, guardrails and lights, with lane closures overnight on Tuesday and Wednesday. In 2001, the bridge had been fitted with a computerized anti-icing system that sprayed chemicals on the surface during winter weather, according to documents posted on the Minnesota Department of Transportation’s Web site.

Eighteen construction workers were on the bridge when it collapsed, said Tom Sloan, head of the bridge division for Progressive Contractors Inc., in St. Michael. One was unaccounted for. The crew was placing concrete finish on the bridge for what he called a routine resurfacing project.

“They said they basically rode the bridge down to the water. They were sliding into cars and cars were sliding into them,” he said.

The school bus had just crossed the bridge when the entire span of Interstate 35W crumpled into the river below. The bus stayed on concrete, and the children were able to escape unharmed out the back door.

Christine Swift’s 10-year-old daughter, Kaleigh, was on the bus, returning from a field trip to Bunker Hills in Blaine. She said her daughter called her about 6:10 p.m.

“She was screaming, ‘The bridge collapsed,'” Swift said. All the kids got off the bus safely, but about 10 of the children were injured, officials said.

The bridge is blocks from the heart of Minneapolis, near tourist attractions such as the new Guthrie Theater and the Stone Arch Bridge. As the steamy night progressed massive crowds of onlookers circulated in the area on foot or bicycle, some of them wearing Twins T-shirts and caps after departing Wednesday night’s game at the nearby Metrodome early.

Thursday’s game between the Twins and Kansas City Royals was called off, but the Twins decided to go ahead with Wednesday’s rather than sending about 25,000 fans back out onto the congested highways. Inside the stadium, there was a moment of silence to honor victims.

The steel-arched bridge, built in 1967, rose 64 feet above the river and stretched 1,900 feet across the water. It was built with a single 458-foot-long steel arch to avoid the need for piers that might interfere with river navigation. The depth of the water underneath the bridge is between 4 to 14 feet, according to the Army Corps of Engineers.