Minneapolis engineers found no sign of trouble during their last inspection of the 18 sets of cables that support the Martin Olav Sabo Bridge and make it a striking landmark over Hiawatha Avenue.
Five months later, a cable broke loose from the top of the span and fell about 100 feet onto the bridge.
No one was hurt when the cable fell Sunday night, but safety concerns prompted the bridge's closure, re-routing traffic, interrupting Hiawatha light-rail service and sending more than 20 city workers on overtime to shore up the bridge.
Those disruptions continued into Tuesday morning.
The $5.1 million, 2,200-foot bridge opened in November 2007 as Minnesota's first cable-stayed bridge, offering bicyclists and pedestrians an alternative to dodging traffic on Hiawatha Avenue. The most recent inspection, in September, turned up "nothing we saw that got anyone's attention, so we are just as surprised as anybody," said Mike Kennedy, director of transportation, maintenance and repair for Minneapolis Public Works.
A pedestrian came across a cable on Sunday night and reported it to the city, said Kennedy. The set of cables that failed are the bridge's longest and reach to the very top of the tower.
Kennedy predicted it will be "some time" before the bridge reopens. He said it was too early to speculate about the cause.
City workers erected several timber and steel columns, known as shoring structures, to support part of the span near the rail line on Monday, but Kennedy said work was moving "very, very slowly."