BROOKLIN – A dog was credited Tuesday with waking two people shortly after midnight when a fire broke out in the attic stairwell of their Route 175 home.

Brooklin Fire Chief Matt Allen said tenants Kimberly Allen and Dana Carter likely would not have awakened had their dog not started barking. There was no working smoke detector in the house, he said.

“It’s an old Cape home, and they go up quick,” Allen said. He added that the smoke would have been toxic in another 15 to 20 minutes. “If they hadn’t woken up when they did, they probably would have expired,” he said.

Allen said roughly 40 firefighters from Blue Hill, Brooklin, Brooksville, Deer Isle and Sedgwick fought the fire, which was limited to the attic stairwell. He said the fire was extinguished approximately 30 minutes after firefighters arrived at the home, which is about one mile south of the Blue Hill town line. A thermal imaging camera owned by Brooksville was helpful in making sure the fire was out, he added.

Allen said the cause of the fire had not been determined Tuesday. An investigator from the State Fire Marshal’s Office will examine the home today, he said.

The home was not insured, according to Allen. He said he is cousin of both Kimberly Allen and the owner of the house.

The couple was put up in a motel for the night by the local chapter of the Red Cross, Allen said. He said no one was injured in the fire.