Divers found more bodies in cars submerged in the Mississippi river yesterday but about 30 people were still missing as commuters told dramatic stories of the rush-hour collapse of an eight-lane motorway bridge in Minneapolis.

Dazed drivers described how their vehicles suddenly went into freefall as the 1,907ft (581m) bridge on Interstate 35 West plunged into the river 60ft below the bumper-to-bumper traffic shortly after 6pm on Wednesday.

“I slammed on my brakes and saw something in front of me disappear and then my car pointed straight down and we fell,” said Dennis Winegar, whose car fell 50ft and landed on another vehicle.

“Boom! Boom! Boom! And we were just dropping, dropping, dropping, dropping,” his wife, Jamie, said.

The official death toll of four was rising yesterday as more bodies were found. But dozens of people – including 52 children on a school bus that had just crossed the river on the way back from a swimming day trip – had lucky escapes.

Nina Jenkins, one of the children on the bus, said that the bus “kind of went up and then it just dropped. The driver went fast so she could get over the bridge.”

Officials said the fact that some lanes were closed for resurfacing work probably saved lives by restricting the number of vehicles on the bridge. But as many as 50 vehicles were still in the 7ft-deep water and police said that between 20 and 30 people were missing. Six of the 79 admitted to hospital had life-threatening injuries.

“There’s no question that the fatality number will go up,” Tim Pawlenty, the Governor of Minnesota, said. “We know there are a number of cars in the water that we haven’t been able to get to and they’ve been there submerged since [Wednesday] evening.”

Rescuers were checking number-plates on submerged cars yesterday to try to identify potential victims.

“The recovery involving those vehicles and the people who may be in those vehicles is going to take a long time,” Police Chief Tim Dolan said. “We’re dealing with the Mississippi river. We’re dealing with currents, and we’re going to have to do it slowly and safely.”

The bridge lies only a few streets away from the heart of Minneapolis, near tourist attractions such as the Guthrie Theatre and the Stone Arch Bridge, and links the two sides of the University of Minnesota campus. A baseball game between the Minnesota Twins and the Kansas City Royals went ahead at the nearby Metrodome about an hour after the bridge collapsed because the organisers did not want to crowd the area with onlookers by sending fans home early.

Drivers said that traffic was crawling across the bridge at 10mph because of the lane closures when the main 500ft span collapsed. The disaster was captured by a security camera, which recorded the roadway buckling and then crashing into the river in a cloud of dust. Mr Pawlenty called it a “catastrophe of historic proportions”.

“The bridge started falling, cars were flying everywhere, and I saw the water coming up,” said Catherine Yankelevich, who climbed out and swam ashore after her car was thrown into the river. “It seemed like a movie; it was pretty scary.”

Janet Stately, who was driving home with her daughter, told CNN: “I heard a horrible noise and then I looked and it seemed like a piece of the bridge was pancaking and going down. Then there was another section that went down in a V, and all the cars were going down into the water like they were tiny toy cars.”

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