The front page of the Minnesota Dep. of Transportation (MnDOT) website provides suggested detours around the collapsed bridge over the Mississippi on Interstate 35 West that had linked Minneapolis and St. Paul.

The 40-year-old span failed last night, buckling during rush hour. According to CNN.com, the collapse has so far led to the confirmed deaths of 4 persons, injuries to at least 79 and reports of 20 to 30 missing persons. CNN.com reported today that officials have stated up to 50 vehicles were in the rubble of the collapsed bridge and it could take five or more days to search the wreckage.

Jim Burnett, former chairman of the National Transportation Safety Board (NYSB) told the Star-Tribune newspaper that investigators will likely focus on two primary causes for the collapse-- vibration and fatigue cracking. The newspaper also reported that a 2005 federal study found the bridge structurally deficient and Burnett told the Star-Tribune that such a designation might indicate a bridge “might be one not adequate for the traffic it takes, but not necessarily dangerous… But a lot of structurally deficient bridges are dangerous."

The steel-arched bridge was built in 1967. It rose about 64 ft above the river and spanned 1,900 feet across the water, according to CJAD NewsTalk radio station, which related the bridge was built with a single 458-ft-long steel arch to avoid putting any piers in the water that might interfere with river navigation.

The site of the collapse is just downstream from the St. Anthony Falls locks and dams. The massive rubble is of course preventing barge traffic from moving up or down the river.