AUBURN — Electrical failure was blamed for a fire that destroyed a four-unit apartment building at 18 Hazel St. early Wednesday, fire officials said Friday.

Christopher B. Stanford, senior investigator at the Office of State Fire Marshal, said the fire started in the master bedroom of a first-floor apartment.

Firefighters responded to 911 calls shortly before 5 a.m. to find the first and second floors at the back of the building heavily engulfed in flames, Deputy Fire Chief Matthew Fifield said.

All the tenants got out safely, helped by other tenants. One tenant suffered a minor burn that didn’t require medical treatment.

A firefighter was taken to a Lewiston hospital with heat exhaustion.

The fire displaced a dozen people; one tenant was helped by the American Red Cross to find housing.