LAWRENCE (CBS) -- A three-alarm blaze tore through a building at East Haverhill and Prospect Streets Tuesday afternoon, Lawrence Fire officials said.

The fire started in a five-unit residential building shortly after 1 p.m.

A building neighbor saw some of the destruction the fire caused.

"All I saw was a big ball of smoke and then the fire and I saw the roof come down," Julio Brito said.

WBZ-TV's Paul Burton reported that all occupants of the building got out safely. One firefighter was taken to the hospital with a minor injury.

Cell phone video showed the intensity of the blaze. At one point, firefighters discovered a mother on the third floor.

"We did find a woman on the right side of the house. Crews helped evacuate her out and then we continued with the firefighting effort. It's an old building, a balloon frame," Lawrence Fire Chief Brian Moriarty said.

Smoke and flames billowed out for hours as firefighters scrambled to contain it. One woman suffered a seizure outside and was transported to the hospital.

Lawrence Mayor Daniel Rivera commented on the neighborhood and damaged building.

"It's an important intersection in the city. It's a building I just got redone. It looked beautiful," Mayor Rivera said.

More than 20 people, most of them children, now find themselves without a home.

"I feel sad for them. I will try to help them. I live around here. They need help. The kids will need clothes."

The building is a total loss. The cause of the fire remains under investigation.