FAIRFIELD — A fire that displaced four tenants from their homes early Sunday morning was intentionally set, authorities said Monday.

Fire started in a barn storage area at 16 Summit St., then spread to the attached five-unit apartment building around 3 a.m. Sunday. The blaze left the tenants of two apartments — two adults in one unit and an adult and child in another — homeless. A cat also died in the fire.

An investigator with the Office of State Fire Marshal went to the fire scene Sunday.

Shannon Moss, public information officer for the state Department of Public Safety, said in a news release Monday that investigators determined the fire was intentionally set, and the incident remains under active investigation.

Only two of the five-units of the building were occupied.

Fairfield Fire Chief Travis Leary said the fire started in the barn storage area then spread into the unoccupied third floor and attic of the apartment building. Flames and smoke were visible at the property before firefighters arrived, he added.

Firefighters knocked the fire down before it spread to the lower floors, and the tenants on the first and second floors escaped unharmed.

Leary said the building could be a total loss because of smoke and water damage throughout.

The American Red Cross was helping the displaced tenants find temporary places to stay.

The chief said he did not think the tenants had renters insurance but that the building itself was covered by the landlord’s insurance.

Fairfield assessing documents indicate the building — which was built in 1900 and has 18 rooms, including eight bedrooms — is owned by a limited liability corporation based in Waterville.

Firefighters from Albion, Clinton, Oakland, Skowhegan, Waterville and Winslow joined the Fairfield department in fighting the fire and were at the scene for nearly five hours.

Fairfield police and a crew from Delta Ambulance responded as well.