PITTSFIELD — A fire late Monday sent a woman to the hospital with burns, destroyed her craft shed and caused extensive damage to her house on Somerset Avenue, Pittsfield fire Chief Bernie Williams said.

“The fire started in a ‘she-shed,'” Williams said Tuesday. “It was at one time a one-car garage and she turned it into a crafting place. The cause is still undetermined but it definitely started in that building because of being out back of the house.”

The 12-by-18-foot wooden shed with a metal roof was destroyed and had collapsed before firefighters arrived, he said. It was located about 4 feet from the main house at 173 Somerset Ave., and the fire spread to the back of the house and into the woman’s bedroom, Williams said. From there, it spread into the rest of the house, which was 1 1/2 stories with an attic, he said. Everything inside was destroyed.

The woman suffered burns mostly to her hands and face and was taken by ambulance initially to Sebasticook Valley Hospital in Pittsfield, Williams said. He declined to identify the woman by name but estimated she was in her late 50s and said she lived alone in the house.

The state fire marshal’s office was called shortly after 11 p.m. Monday to help determine the cause of the blaze, Williams said. Officials don’t know if she was in the house when the fire broke out. It was reported at 10:30 p.m., he said, and firefighters remained on the scene until about 3 a.m. Tuesday.

“It was called in probably by her, but they took a minute to figure out what she was saying,” he said. “She wasn’t totally coherent. By that time, somebody saw the fire and called it in.”

Two dogs that lived at the home are OK and are being cared for by a next-door neighbor, Williams said.

Shannon Moss, public information officer for the Maine Department of Public Safety, said Tuesday that the investigation revealed the fire started in the outbuilding, and it’s believed the homeowner was in or near the shed at the time of the fire.

Moss said the woman was scheduled to be taken to Maine Medical Center in Portland.

The fire remains under investigation, she said.

About 25 firefighters from Pittsfield, Hartland, Detroit, Plymouth and Newport fought the fire and the Pittsfield Police Department also was on the scene. Central Maine Power Co. shut off power to the house, Williams said.

The fire inside the house was very hot, he said. The home had been retrofitted inside over the years, and there was a partition in the attic that went from one end to the other, he said.

“Because the fire got such a start and nobody saw it, it created a huge amount of heat,” he said. “The aluminum siding was melting and by the time my first two guys were on scene, the aluminum siding was gone and clapboards were burning on the house.”

Williams described the house as having a lot of castle-like turrets and dormers — an old house likely built around 1900.

“Once the fire got inside the house, it just went everywhere,” he said. “Partway through the thing, we were still trying to get entry. There was a lot in there. There was a huge amount of fire in the house you couldn’t see from the outside.”

At one point, someone at the scene reported people were living on the second floor, but that turned out not to be the case, Williams said. He was told they had moved out a week earlier, which he said was fortunate because they would likely not have survived if they were inside.

Williams described the house as having extensive damage to the rear and heat and water damage to the front. He said he is not sure if the property is insured.

The house is located just outside the downtown on Somerset Avenue. Its backyard overlooks Mill Pond, which was created years ago for two woolen mills that were on site, as well as a lumber operation that used the pond to float logs in, Williams said.