FITCHBURG, MASS. >> Authorities say a second woman who was inside a multi-family Fitchburg home when it caught fire has died.

Firefighters responded to the Walton Street home just after midnight Wednesday and found flames on the second floor at the building's rear.

One woman, identified by authorities as Janice Oikelmus, was found unconscious and her sister was found dead. Their brother, 60-year-old Steven Oikelmus, was also found in the home and remains in critical condition.

Officials say 58-year-old Oikelmus was taken to a hospital where she died Wednesday night. The identity of her sister hasn't been confirmed.

A spokeswoman for the state fire marshal's office says a battery was found on top of a smoke alarm inside the home.

The cause of the fire remains under investigation but is not considered suspicious.