ORANGE — Four people were displaced Wednesday morning when a fire damaged a single-family house at 86 Mechanic St.

The Salvation Army Athol Corps is reportedly assisting Donna and Kevin Sweeney and their sons, Sean and Nicholas, following the blaze that was called in at 9:52 a.m. after starting in a second-floor bedroom.

Orange Fire Chief James Young said Wednesday afternoon that there was not a determined cause of the fire yet, though he said it was accidental in nature. Young said the fire is being investigated by his department as well as the state Department of Fire Services.

“[Firefighters] did a great job, a very quick knockdown of the fire that originated in a room on the second floor,” Young said at the scene.

Nicholas Sweeney was home alone, asleep on the couch when he awoke to smoke and flames. He said he called 911 and exited the home with his black Labrador retriever. His 11-year-old daughter was in school at the time. The family cat, meanwhile, was not accounted for at the time of the fire.

Sean Sweeney, like his parents, was at work when the fire started. He arrived after the fire was brought under control.

Firefighters responded from Orange, Athol, New Salem and Phillipston, among other area towns. Young said one of his firefighters suffered a minor hand laceration, was treated at a hospital and released.