ordered states to immediately inspect bridges of similar designs. Transportation Secretary Mary Peters said Saturday that those inspections hadn't fo

ordered states to immediately inspect bridges of similar designs. Transportation Secretary Mary Peters said Saturday that those inspections hadn't found any immediate problems.

Reports and inspections over the years had raised alarm about the Minnesota bridge, including rust-eaten steel beams, missing bolts and cracks in the welding that held load-bearing parts together.

A consulting company that thoroughly examined the bridge noted that one possible fix — steel plating of fractures — carried a "relatively high cost," according to a January report. Transportation officials deny that cost pressures swayed their decisions.

Authorities and engineers agree that the truss-style design of the bridge played a big role in the relatively low number of fatalities. The steel that supported the bridge was below the structure — as opposed to above the span in more traditional bridge designs.

"I think that was a lifesaving feature," Schofer said. "They had this huge advantage. They weren't crushed by steel."

Clack also praised the rescuers who rushed to the bridge in the chaos after the collapse. Because the bridge was near the heart of downtown, several emergency crews and residents were close by.

Though the collapse occurred during rush hour, the heavy traffic meant the cars were almost stopped and didn't have much momentum, so the collapse was less likely to hurl moving cars into the river, Clack said.

"When the bridge fell, they went straight down," he said.

Mark Rosenker, chairman of the National Transportation Safety Board, said investigators were particularly interested in learning why a part of the bridge's southern span shifted as it collapsed. That was the only part of the bridge that shifted, and it could help pinpoint the cause.

The irregular slope of the riverbank on the south side of the bridge turned out to be a good thing. When that portion of bridge snapped at the middle, the support pylons held, and the roadway only had a short distance to fall until it was caught by a drop-off just before the river.

On the north side of the bridge, however, the bank slopes down in a steady angle to a broad flood plain. When that portion of the bridge crumpled, there was nothing to catch it.

Dr. John Hick, assistant medical director for emergency medical services at Hennepin County Medical Center, said injuries on the north end of the bridge were much more grave.

Another factor that may have limited the death toll is the behavior of the river itself.

Scott Bratten, who regulates locks and dams on the river for the Army Corps of Engineers, said that because of the drought in Minnesota, the water was flowing at just a third of its normal speed. That may have made it easier for people in cars to escape them, and it almost certainly made it easier for rescuers to make their way into the water and help the dazed and injured.

"During the spring it's a raging torrent in there and it would be a very dangerous place," said Whitney Clark, executive director of Friends of the Mississippi River. "The low water I'm sure was a factor in not making currents very much of an issue. ... If this had happened during the spring snowmelt or something it would have been a much different situation."

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Associated Press writers Matt Crenson, Henry C. Jackson, Brian Bakst and Martiga Lohn contributed to this report.