CHICAGO -- Three people were crushed to death and two critically injured when scaffolding from the landmark John Hancock Building fell onto their cars on a busy downtown street Saturday, a fire department spokesman said.

Unusually high winds -- gusts of up to 58 mph were recorded at a downtown airport around the time of the collapse, just before 2 p.m., the National Weather Service said -- may have caused a 25-foot section of scaffolding to fall from the 43rd floor, fire officials said.

"We can only speculate wind had something to do with it," Fire Department Cmdr. Tim Stokes said.

Officials said they believe the scaffolding was on the west side of the building, then swung away before falling onto three cars waiting for a stop light on the south side of the building.

Scaffolding also shattered dozens of windows in the Hancock building, and a window in the Westin Hotel lobby, north of the Hancock building, officials and witnesses said.

Glass rained down to the streets below, which are typically bustling on the weekend with thousands of residents and tourists, and debris was hanging from trees.

One woman was in critical condition and two were in good condition at Northwestern Memorial Hospital.