As divers search the river for submerged vehicles and bodies trapped beneath the twisted debris of the I-35W bridge, finger-pointing has already begun over a federal report two years ago that found the bridge was "structurally deficient."
Several teams of investigators are examining the evidence on what may have caused the eight-lane Interstate 35W bridge to .
"It's hard to be conclusive so early, but it looks like the main support, the main steel arch, may have given way or something right near it," Richard Stehly, an expert in bridge engineering and co-founder of St. Paul, Minn.-based American Engineering Testing, told CBS Evening News anchor Katie Couric.
"Also, the things that support the main arch, the foundations on either bank, perhaps they did. But investigators will look at everything. They will look at the materials. They will look at all the pieces of debris. And they'll find out the cause, because we need to learn the reason for its failure."
Inspections as far back as 2000 on the bridge identified both corrosion in the steel and a lot of cracking, says Stehly.
Questions are also being raised about a 2005 report in the U.S. Department of Transportation's National Bridge Inventory that rated the bridge as "structurally deficient" and possibly in need of replacement.
The report said there were fatigued details on the main truss and floor truss system. Yet it concluded there was no need to prematurely replace the bridge because of fatigue cracking, avoiding the high cost associated with such a large project.
When the bridge was built 40 years ago, it was state of the art, a massive steel arch spanning the Mississippi. But the bridge was designed without the extra support common to later designs, which meant that if one component failed, the whole bridge was likely to fall, reported CBS station WCCO-TV in Minneapolis.
Federal officials alerted states Thursday to immediately inspect all bridges similar to the Minneapolis bridge that collapsed.
President Bush, who will travel to the scene of the disaster on Saturday, said the federal government would help rebuild the bridge in the city that will host next year's Republican National Convention.
"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," Mr. Bush said.
Still stung by harsh criticism of the government's sluggish response to Hurricane Katrina, Mr. Bush talked with state and local officials in Minnesota, and the administration dispatched officials to the scene.
The House Transportation Committee quickly approved legislation Thursday that would direct $250 million to Minnesota to help it replace the bridge.
The White House said a U.S. inspection of the 40-year-old bridge in 2005 found problems. The Interstate 35W span rated 50 on a scale of 100 for structural stability and was classified as "structurally deficient," transportation officials said.
The designation means some portions of the bridge needed to be scheduled for repair or replacement, and it was on a schedule for inspection every two years. "It didn't mean that the bridge is unsafe," Transportation Secretary Mary Peters said.