A fire damaged a garage and two homes in Portland’s Riverton neighborhood on Monday afternoon.

The Portland Fire Department was called to the scene of a garage fire extending into a single-family home at 31 Castine Ave. at about 2:40 p.m., Division Chief Sean Donaghue said in a news release.

Firefighters arrived on scene and quickly struck a second alarm, Donaghue said. By about 2:50 p.m. the fire extended to 27 Castine Ave., prompting the response to be upgraded to a third alarm.

The fire was knocked down by 3:05 p.m., Donaghue said, and was considered fully under control about 20 minutes later.

No injuries were reported to occupants, pets or firefighters, Donaghue said, but the American Red Cross is assisting the occupants of both residences.

Traffic on Forest Avenue near its intersection with Castine Avenue came to a standstill Monday afternoon while crews responded. Portland police urged motorists to avoid the area in a social media post. Traffic began moving again by 4 p.m.

All on-duty Portland fire crews responded to the scene, Donaghue said. Firefighters from South Portland, Westbrook, Scarborough, Falmouth and Cumberland provided mutual aid, with some responding directly to the fire and others covering Portland’s stations.

Crews cleared the scene at about 6 p.m., Donaghue said, and the cause is still under investigation.