WESTON, Fla. – A fire prompted an evacuation of the Cleveland Clinic's outpatient clinic building in Weston Friday.

Large plumes of smoke coming from 2950 Cleveland Clinic Boulevard could be seen for miles in Broward County. Matt Weiner was in a moving vehicle when he spotted the dark smoke.

"I've never seen anything like this in my life," Weiner said on Twitter. He posted a video.

Sky 10 was above the hospital as firefighters were dousing the roof of an annexed building under construction. The fire started about 12:30 p.m., Cleveland Clinic spokesperson Stacy Merrick said in a statement.

A roofing company was working Friday morning, but when the fire started the workers had taken a break for lunch.

Just as Broward Sheriff's Office fire station 81 rolled up on the fire there was a large explosion that rocked the area and fire officials believe a 100 pound propane tank the roofing company was using exploded.

As a precaution the hospital evacuated their near by outpatient clinic building. Hundreds of patients, doctors, nurses and other health professionals were outside for about an hour. Employees said they were allowed back in the building about 1:50 p.m.

Investigators believe the cause of the fire was accidental.

The construction is part of a $60 million project: A five-story, 143,000 square foot building. It will be named the Egil and Pauline Braathen Facility. And it will house the expanded Pauline Braathen Neurological Center and Cleveland Clinic Florida's Cancer Center. Braathen donated $30 million in 2013 for its construction.

"That area houses some very specialized equipment fortunately none of that equipment appeared to sustain any damage," Broward Sheriff's Office Division of Fire-Rescue spokesman Mike Jachles said. "Our fire fighters were able to get in there quickly and place tarps over the equipment and protect it."

No one was injured. And firefighters extinguished the flames by 1:30 p.m.

"It was a very impressive fire," Jachles said. "You could see it from miles away on the Interstate. It was a lot worse than it looked."

Local 10 News Peter Burke, Kathleen Corso and Liane Morejon contributed to this story.

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