BOSTON -- A fire caused extensive damage Thursday at a former church in South Boston that was converted into apartments.

NewsCenter 5's Steve Lacy reported that no one was injured in the fire at 55 West Broadway. After a preliminary investigation, officials said that careless disposal of a cigarette may be to blame.

"As soon as we came out, we ran to this side of the sidewalk, and we saw fire coming out. It was actually fire at the time," tenant Carlos Rodriguez said. "They were already trying to put it out."

The fire caused heavy damage to a penthouse unit, forcing firefighters to break through the building's slate roof.

"The roof is slippery, and it is tough when guys are up there trying to keep their footing," a fire official said.

The building dates back to the 1840s. The Archdiocese of Boston sold the church in 2000, and it was converted to condos four years later.

"These are the original tiles that were put on from Italy, so we are sorry to see the fire up there," said Paul Henry, head of the condo association.

Officials said that they'll take a close look at the building's fire alarm.

"When we arrived, we had to manually pull the alarm," a fire official said.

Police shut down West Broadway from A Street to Dorchester Avenue during the morning commute.

Nine people were displaced by the fire, officials said.