LIMESTONE, Maine — Investigators from the state fire marshal’s office are working to determine what sparked a suspicious early morning fire Thursday that swept through an apartment building, leaving 20 people homeless.

Limestone police said in a statement Thursday afternoon that while one of the officers was helping to evacuate the scene, he was told that the fire might have been deliberately set.

Tim Lowell, senior investigator with the agency, said that there is a “person of interest” in the case but no one had been arrested as of Thursday evening. He said that the fire began in the kitchen of a first-floor apartment but he did not reveal an ignition source or say whether the person of interest lived in the apartment complex.

Firefighter Jon Cote of the Limestone-Loring Fire Department said Thursday that the blaze began just before 3:30 a.m. at 23 Main St.

Firefighters from Limestone and Fort Fairfield went to the apartment house and had the fire out in approximately two hours, Cote said. He was not sure how many apartment units were in the building, but he believed 20 people were affected.

Four people were able to go back into the building after the fire to retrieve some possessions.

According to police, who helped evacuate the residents from the building, the blaze appeared to be concentrated in one of the apartments on the first floor of the two-story building.

Cote said that investigators are trying to determine what sparked the blaze.

The Pine Tree Chapter of the American Red Cross has stepped in to help the occupants, who are being put up at motels.

The Limestone Police Department assisted at the scene.