Hundreds of pounds of scaffolding equipment came crashing down onto a busy Loop street during the Tuesday afternoon rush, damaging a car and shutting down traffic near Millennium Park.

Emergency crews were called about 2:15 p.m. to the Crain Communications Building at 150 N. Michigan Ave., where a window-washing crew’s equipment came loose from an ornamental portion of the high-rise and went tumbling down just north of Randolph Street, according to Chicago Fire Dept. Special Operations Chief Tim Walsh.

The debris smashed eight windows on the building and damaged a car on Michigan, Walsh said. Chicago Police had said one person was injured by the debris, but Walsh said that case was unrelated.

Greg Phelps said he and his coworkers in a 39th-floor office heard the metal cables bouncing off the glass most of the day until they heard a loud snapping crash.

“Then we just saw cables sliding really fast down the side,” he said.

A pane of glass is smashed on the 39th floor of 150 N. Michigan Ave. after scaffolding came loose Tuesday afternoon. | Photo provided by Greg Phelps

The equipment that fell is called a davit — a piece of aluminum that secures scaffolding cable as the platform moves up or down. Crews worked into Tuesday evening trying to secure a 300-pound hunk of the fixture as it swung shakily from the edge of the building near the 10th floor.

“Until we do that, because the davit is just handing there precariously, it’s not secured anywhere, we want to make sure that no one walks through the area,” Walsh said.

Traffic on Michigan was shut down between Randolph and Lake, tying up traffic for blocks. Hundreds of pedestrians stopped to gawk outside police crime scene tape blocking off the normally bustling intersection.

Metal and cable equipments litter the sidewalk outside 150 N. Michigan Ave. after a scaffolding collapse Tuesday afternoon. | Photo provided by Greg Phelps

Metra commuters headed to Millennium Station were being told to use a nearby pedway to enter the station in place of the Randolph Street entrance during the Tuesday evening rush.

Curious onlookers gave the crew some light cheers and golf claps from across the street when workers secured the L-shaped beam a little after 4:30 p.m. and wrangled it inside the building.

The city Buildings Department is investigating what led to the fall.

Crews secure a 300-pound beam that was dangling from the 10th floor of 150 N. Michigan Ave. on Tuesday. | Mitchell Armentrout/Sun-Times

Crews secure a 300-pound beam that was dangling from the 10th floor of 150 N. Michigan Ave. on Tuesday. | Mitchell Armentrout/Sun-Times