PITTSBURGH — An unsafe 110-year-old Pittsburgh bridge was demolished in less than a second, sending a huge cloud of dust in the air and breaking windows in a dozen homes.

About 400 Pittsburgh residents nearby were evacuated before demolition crews used about 70 pounds of explosives to implode the Davis Avenue Bridge at 2:02 p.m. Wednesday.

The mayor's office said 12 homes were damaged, mostly with broken windows. All but three of the damaged homes are on Woods Run Avenue, which runs directly beneath the bridge. The city contracted with a glass company to replace the windows. City representatives plan to visit the homes today to address remaining concerns.

The overpass closed to vehicles in 2001, but a consultant said it could collapse soon.