The fire was reported at about 2:25 a.m. Sunday at a two-story, wood-frame house on Taunton Avenue. The fire was ruled an accident, said State Fire Marshal Stephen Coan.
Authorities did not release the identities of the three, but neighbor Michelle Shaw told The Boston Globe that Theresa Kane, 79, and her daughters, Jayne, 54, and Cheryl, who was in her mid-40s, all lived in the house.
Jayne, who worked in a nursing home, cared for her sister, who was mildly retarded, and her mother, who was in ill health, Shaw said.
``I couldn't see any of them living without the other,'' she said.
Coan said the victims had been sleeping in three beds in the first-floor front bedroom. He said there were no smoke detectors in the home.
Seekonk Fire Chief said firefighters had trouble opening the door because the bodies of one of the women was leaning against it. The bodies of the other two were still in their beds.
He urged people to install smoke detectors and to make sure they had live batteries, noting that no working smoke detectors had been found after another fire two weeks ago in the Cape Cod town of Dennis that killed five people.