Bridge collapses in Minneapolis

The bridge was undergoing nonstructural re-decking work, U.S. Transportation Department spokesman Brian Turmail said.

A 2001 study conducted by the Minnesota Department of Transportation found "several fatigue problems" in the bridge's approach spans and "poor fatigue details" on the main truss.

The study suggested that the design of bridge's main truss could cause a collapse if one of two support planes were to become cracked, although it allowed that a collapse might not occur in that event. But, the study concluded, "fatigue cracking of the deck truss is not likely" and "replacement of the bridge ... may be deferred."

Two years ago, the U.S. Department of Transportation's National Bridge Inventory database said the bridge was "structurally deficient."

The bridge received a rating of 4 on a scale of 0 to 9. A bridge receives a rating of 4 when there is "advanced section loss, deterioration."

About 140,000 cars a day travel over the bridge, according to the Minnesota Department of Transportation.