NEWPORT, Maine — Tenants in an Elm Street apartment building escaped injury after a morning fire on Saturday.

Fire crews from Newport, Pittsfield and Corinna responded to a structure fire at 99 Elm St. Crews received the call at 6:48 a.m., according to Newport fire Lt. Amanda Chretien.

The fire started on the second floor and spread to the first floor, she said.

“We’re unsure of the cause at this point. It appears it started with the heater,” said Chretien. “[The fire] went down into the walls and the flames got stuck between the first and second floor. That was a challenge. We had some fire drip down from the second floor and ignite a Christmas tree on the first floor. We were dealing with multiple fires.”

Chuck Burrill, a tenant on the second floor, said he was awoken by his girlfriend as she smelled smoke.

“She woke me up and I thought maybe we left something like the kettle on,” said Burrill. “I went to open up the windows, and then I noticed smoke bellowing up from underneath the register behind the couch.”

First floor tenant Mark Lawrence said there are four people living in the building. No one was hurt.

Chretien said the fire was trapped in the floor and walls.

“It was difficult. It’s been renovated so many times that there are floors, subfloors and three different walls between those,” she said. “It took a while to get between all that.”

It took approximately 20 minutes to knock down the fire, Chretien added.

“It was great teamwork on a cold day,” she said.

The state fire marshal’s office will be called to determine the cause of the fire, said Chretien. The American Red Cross is being contacted for the families affected by the fire.

Sebasticook Valley Health Ambulance and the Newport Police Department assisted at the scene.