FAIRFIELD — A mother and her adult son lost their Hutchins Road home to a fire late Tuesday.

Fairfield Fire Chief Duane Bickford said a neighbor called and reported flames showing from the house at 9:40 p.m. The woman and her son were out of the house and uninjured when fire crews arrived at 9:55 p.m. Fire crews left the scene around 4 a.m. Wednesday, he said.

The fire is thought to have started in the chimney area, and fire marshals are tentatively calling the fire accidental, Bickford said.

He said the family’s last name was Hutchins, but he did not know their first names.

The bitter cold made combating the late-night fire a challenge, Bickford said.

A school bus was sent to the scene and left running with the heat on, and fire crews used it to warm themselves in shifts between stints fighting the fire.

“It was very difficult,” he said.

Bickford said fire crews kept the water running to prevent freezing problems with the hoses.

About 25 firefighters from eight towns, including Fairfield, responded to the fire.

The American Red Cross also was called to the fire and set the residents up with a hotel for the night.