Rescue officials in Minneapolis said the effort to recover the dead from Wednesday's bridge collapse cannot be rushed on the second day of stop-start searches in the dark, swirling waters of the Mississippi River.

As the first of the four confirmed victims of the disaster were identified, Hennepin County Sheriff Richard Stanek said that the teams of police divers trying to reach the submerged wrecks of dozens of vehicles, some crushed under tons of concrete, were having to move with extreme caution.

The US Army Corps of Engineers has lowered the level of the river by 30cm to aid the recovery operation but new eddies caused by the fallen debris prompted Mr Stanek to say that conditions in the water, which in some places is up to 14ft deep, were "even more treacherous" today than yesterday.

Mr Stanek said that today's dives would focus on four partially submerged cars that were checked in the first moments after the collapse and nine other "targets" identified by sonar scans of the river. Other targets inspected yesterday included vehicle wreckage and pieces of concrete.

Laura Bush, the First Lady, will also visit the scene of the rush-hour disaster in downtown Minneapolis today, before President Bush arrives tomorrow. The failure of the 40-year-old bridge has prompted the inspection of thousands of similarly-worn structures across America which will cost billions of dollars to repair.

The death toll rose to five when one body was recovered at the scene yesterday, although officials estimate that eight remain in the rubble. The body of a man was found in the cabin of an articulated lorry that burst into flames during the collapse.

The other four people killed when the Interstate 35W bridge fell just after 6pm on Wednesday were identified today as Sherry Engebretsen, Julia Blackhawk, Patrick Holmes, and Artemio Trinidad-Mena.

Ronald Engebretsen said his family was trying to come to terms with the death of his wife, who was 60. "She’s a great person. She’s a person of great conviction, great integrity, great honesty and great faith in her God," he said.

The Mexican Government confirmed the death of Artemio Trinidad Mena, a 31-year-old vegetable salesman, who was on his way home from work when the eight-lane bridge gave way. Abundia Martinez, his widow, told Radio Formula that he was an illegal immigrant who had been living in Minneapolis for ten years.

"We’re asking for financial help mainly because my children are in Mexico and I have a little girl here and more importantly because we want to send my husband’s body to Mexico," she said.

There were reports that a 23-year-old mother and her 2-year-old daughter are among those feared to have died in the collapse. Sadiya Sahal, who was five months pregnant, last spoke to her family half an hour before the disaster, saying that she was stuck in traffic on the bridge. Her daughter, Hanah Mohamed, was in the back seat of the car. "Her husband is destroyed. He’s in shock," said Omar Jamal, a spokesman for the family.

The collapse of bridge 9340, as it was officially known, has prompted questions about the safety of thousands of other bridges officially rated as "structurally deficient" by US infrastructure inspectors but allowed to stay in place with running repairs.

The bridge was first designated as deficient 17 years ago — a rating it shares with more than 70,000 bridges in America and 1,160 in the state of Minnesota alone — but was not scheduled to be replaced before 2020. The American Society of Civil Engineers said it would cost $188 billion and 20 years to bring all the other structurally deficient bridges in the country up to standard.

Federal transport officials have alerted local inspectors to the existence of 756 steel-trussed bridges similar to the one that failed in Minneapolis, while the state of Minnesota, and several others have ordered a review of their inspection techniques. Built according to now outdated safety rules, bridge 9340 had little redundancy in its design, meaning it was vulnerable to the failure of a single piece of the structure.

The investigation into Wednesday's disaster — the first major bridge collapse in America since 1983 — is expected to focus on fatigue cracks, vibration and corrosion in the steel joints that held the bridge's criss-crossing members as well as the maintenance work that was taking place on the bridge at the time of the fall.

Structural experts say that sudden collapses are often found to be caused a combination of underlying factors and momentary aggravations, such as traffic flow at the time of the failure. Investigators will also examine the progression of the collapse, and ask why so much of the bridge gave way.

Corrosion in the bridge's bearings was first identified in 1990, leading to its "structurally deficient" rating, but a series of inspections and repairs, including plates bolted over a crack four-feet-long, allowed Minnesota's busiest bridge to continue in service. "We thought we had done all we could," said Dan Dorgan, one of Minnesota's state bridge engineers by the wreckage. "Obviously something went terribly wrong."

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