Five people were injured Wednesday when scaffolding fell from a high-rise in downtown Miami, while a sixth person died of a heart attack while fleeing the falling debris, authorities said. 

The collapse occurred Wednesday afternoon at the Echo Brickell building, a 60-floor condominium tower.

Miami Mayor Tomas Regalado told reporters that injuries related to the collapse were minor. 

"Some woman was driving a car that was smashed," Regalado said. "Some people were injured as they were walking in Brickell [Avenue] and trying to get away."

The building's developer released a statement saying that a section of formwork fell from the top of the structure and offering thoughts and prayers to the victims. 

The debris forced police to close nearby streets to traffic.

"We were just working at our computers, and all of a sudden heard a very large crash," witness Rudy Tomarchio, who works across the street, told WSVN. "We looked up, and in front of our eyes, we just see all this debris just crashing down ... We saw a couple construction workers in the crosswalk. It looked like they were trying to get out of the falling debris."

Family members identified one of the injured construction workers as 34-year-old Quincy Williams, who suffered a gash on his head. 

There was no immediate word on what caused the scaffolding to fall.