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The Federal Bureau of Investigation donated a three–dimensional laser scanning device that transportation officials began using August 4 to document the wrecked Interstate 35W arch truss bridge now laying across the Mississippi River in Minneapolis.

National Transportation Safety Board investigators plan to use images collected from the scan, a partial reconstruction of debris, a recovered surveillance video and an existing computerized analysis of the bridge to model "a very drawn out series" of failure scenarios, says NTSB Chairman Mark V. Rosenker.

"We're really looking at what this computer model will do for us," Rosenker says. "It could be months that we do this. Remember, there are a lot of elements of that bridge."

In addition, the recovered surveillance video "is the equivalent of a flight recorder" of the collapse, says Rosenker. It shows the southern end of the bridge collapsing, followed by the northern end.

"We're beginning to look at that southern end," Rosenker says. "It's interesting to us." As for cause of collapse, the lead investigator reiterated, "We have not ruled out anything."

In the video, the deck and superstructure appear to "split off" in two different directions, Rosenker added. The bridge's concrete deck falls to the east, while its steel superstructure falls to the west.

So far, no pieces of the bridge have been removed from the scene, says NTSB.