BRUNSWICK — An electrical problem is being blamed for a fire that severely damaged a six-unit apartment building on Oak Street on Friday afternoon.

The blaze, which required response from eight fire departments, left 19 people homeless.

Brunswick Fire Chief Ken Brillant said the extra firefighting help was necessary because of the size and older design of the three-story building.

“We needed three ladder trucks, and were pumping off more than one hydrant,” he said.

His department received the first of many calls at 3:40 p.m. Two minutes later, the first units arrived to find fire in all three floors of the building, plus the attic. The fire was concentrated in the back, overlooking an empty lot on Mill Street, and it burned up the siding, out the windows and through the roof.

Brillant said some of the building’s tenants were still inside when firefighters arrived, but they were promptly evacuated.

“No one had to be rescued,” he said.

There were no serious injuries, although one couple and a young child were transported to Parkview Hospital for smoke inhalation.

No other buildings were affected, Brillant said, although firefighters did evacuate a neighboring apartment building because they initially feared the fire could spread next door.

Crowds gathered on Oak and Mill streets to watch firefighters battle the flames. Departments from Brunswick Naval Air Station, Bath, West Bath, Topsham, Freeport, Durham, Lisbon Falls and Orr’s and Bailey Islands assisted. The last fire units left the scene around 8:30 p.m., but Brillant said the fire was mostly extinguished by 6 p.m.

The state fire marshal determined that the blaze was caused by an electrical problem within the walls of the building. Brillant said because the house was “balloon-framed,” a style common in many older houses, there were spaces between the walls that ran from the first floor up to the attic. This allowed the fire to spread quickly.

The Red Cross also responded to the fire, and provided tenants with money for emergency food, clothing, medicine, and vouchers for five-night hotel stays, according to Connie Jones, executive director of the Mid-Coast chapter.

Jones said the number of tenants displaced was even larger than the February fire that destroyed half of a multi-unit apartment building on Union Street. That fire displaced 17 people.

The cost of caring for the Union Street tenants completely depleted the Red Cross’ local disaster relief fund, but Jones said the organization has received approximately $9,000 in donations since then. So far, the Red Cross hasn’t had to dip into other funds to assist the victims of the Oak Street fire, 10 of whom are children.

The Red Cross has assisted 55 people who lost their homes to fires since Jan. 10, which is almost the number of fire victims the agency normally assists in an entire year.

Jones said it is rare to have “two large fires back to back.”

Emily Guerin can be reached at 781-3661 ext. 123 or eguerin@theforecaster.net. Follow her on Twitter: @guerinemily.