A Chicago fire engine was on the top floor of a parking garage at a city health facility Tuesday morning when the garage partially collapsed underneath it, authorities said.

According to Chicago Fire Department spokesman Larry Langford, Engine 126 was responding to a “medical run” at the Symphony of South Shore and the vehicle was left parked on the top floor of a two-story parking garage as firefighters went inside the building.

While they were inside, the deck “failed and collapsed,” Langford said.

The engine went into a hole but the front bumper kept it from falling to the ground level.

An engineer inside the vehicle at the time was able to climb out via a back door, Langford said. That person was initially believe to be uninjured but was later taken to an area hospital for "delayed back pain," officials said.

"We heard a big boom and we didn't know what it was," said Tamika Wilson, who was inside the senior center at the time of the collapse. "We came out, we started looking and that's when they started blocking it off and that's when they told us the roof had caved in."

No one was on the lower level of the garage at the time and no other injuries were reported, according to Langford.

"The situation could have been much worse if this had been large passenger vehicles," CFD tweeted Tuesday afternoon, adding that they were thankful the collpase didn't happen as SUVs were passing in and out. "They most likely would have fallen to the ground."

Authorities were waiting for crews to help remove the vehicle from the garage, using heavy chains and attachments to secure it in its current position.

"I was stunned because I never saw anything like that," Wilson said.

Check back for more on this developing story.