Divers searched the Mississippi River on Thursday for more bodies entombed in cars trapped beneath the twisted steel and concrete slabs of a collapsed bridge. As many as 30 people were missing as the rescue effort shifted to recovery. The official death count stood at four Thursday morning, but Police Chief Tim Dolan said more victims were still in the water. Hospital officials counted 79 more 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 Thursday morning. "We know we do have more casualties at the scene." The eight-lane Interstate 35W bridge, a major Minneapolis artery, was being repaired and two lanes in each direction were closed when the bridge buckled during evening rush hour Wednesday, sending dozens of cars plummeting more than 18 meters into the Mississippi River. As many as 50 vehicles were in the river, many of their occupants having scrambled to shore. The Homeland Security Department said the collapse did not appear to be terrorism-related, but Sheriff Richard Stanek said Thursday that the cause was still unknown. "All indications are that it was a collapse, not an act of someone doing it," Stanek said. He said at least a dozen submerged vehicles were visible in the water. A train had been passing beneath the roadway at the time and it also fell, including a car carrying a chemical, beads of polystyrene, that the fire chief said was not particularly hazardous. Authorities were checking license numbers of the cars in the water. Getting the vehicles out of the water will involve moving around very large, heavy pieces of bridge. "The bridge is still shifting," said Minneapolis Police Chief Tim Dolan. "We're dealing with the Mississippi River. We're dealing with currents. We're going to have to do it slowly and safely." At Hennepin County Medical Center, patients had arrived in a stead stream after the collapse, some unconscious or moaning, some barely breathing, and others with serious head and back injuries, Dr. William Heegaard said. "There was blood everywhere," he said. President George W. Bush offered his condolences to victims and said the federal government would help ensure that the span is rebuilt as quickly as possible. "We in 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," Bush said in the Rose Garden following a Cabinet meeting. Relatives of some of the missing gathered in a hotel ballroom early Thursday, waiting for word on loved ones who couldn't be located. "I've never wanted to see my brother so much in my life," said Kristi Foster, who went to an information center set up at a Holiday Inn looking for her brother Kirk. She had not had contact with her brother or his girlfriend, Krystle Webb, since the previous night. Mayor R.T. Rybak said he expects the death toll to fluctuate throughout the day. "I think you can expect that to be a dynamic situation for a while," he said. Thursday morning, Transportation Secretary Mary Peters announced a $5 million grant to help pay for rerouting traffic patterns around the disaster site. "We fully understand what happened and we will take every step possible to ensure something like this will not happen again," Peters said. The White House said first lady Laura Bush would travel to the city on Friday to console the victims' families. Senator Amy Klobuchar said up to $100 million in federal funds will be available for rebuilding and recovery. "A bridge in America just shouldn't fall down," Klobuchar said. "That's why we have called for this investigation." Gov. Tim Pawlenty said the bridge was inspected by the Minnesota Department of Transportation in 2005 and 2006 and that no immediate structural problems were noted. "There were some minor things that needed attention," he said. "They notified us from an engineering standpoint the deck might need to be rehabilitated or replaced in 2020 or beyond," Pawlenty said Wednesday. The 40-year-old bridge was rated as "structurally deficient" two years ago and possibly in need of replacement, the Star Tribune reported. The newspaper said that rating was contained in the US Department of Transportation's National Bridge Inventory database. "We've seen it, and we are very familiar with it," Jeanne Aamodt, a spokeswoman for the Minnesota Department of Transportation, said of the 2005 assessment of the bridge. Aamodt noted that many other bridges around the country carry the same designation that the I-35W bridge received. She declined to say what the agency was going to do to address the deficiencies found in 2005. Road crews were working on the bridge's joints, guardrails and lights this week, with lane closures overnight on Tuesday and Wednesday. The bridge was fitted in 2001 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. There were 18 construction workers on the bridge at the time of the collapse, said Tom Sloan, head of the bridge division for Progressive Contractors Inc., in St. Michael. One of the workers was unaccounted for. Sloan said his crew was placing concrete finish on the bridge for what he called a routine resurfacing project. "It was the final item on this phase of the project. Suddenly the bridge gave way," he said. Sloan said his workers described a horrific scene. "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 entire span of Interstate 35W crumpled into the river below. Some injured people were carried up the riverbank, while emergency workers tended to others on the ground. A school bus had crossed the bridge before it collapsed. The bus did not go into the water, and broadcast reports indicated the children on the bus exited out the back door. The collapsed bridge stood just blocks from the heart of Minneapolis, near tourist attractions like 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 after departing Wednesday night's game at the nearby Metrodome early. The steel-arched bridge, which was built in 1967, rose about 19.5 meters above the river and stretched about 580 meters across the water. The bridge was built with a single 140-meter-long steel arch to avoid putting any piers in the water that might interfere with river navigation. The river's depth at the bridge was not immediately available, but the US Army Corps of Engineers maintains a channel depth of at least 2.74 meters in the Upper Mississippi from Minneapolis southward to allow for barge and other river traffic. The site is just downstream from the St. Anthony Falls locks and dams.