Authorities are trying to determine how a 2-year-old girl died and a second young girl was left in critical condition after they were found unresponsive at a home in Massachusetts.

Officials in Worcester (WOOS'-ter) County say the girls' foster mother called 911 around 12:30 p.m. Saturday to report that the two were unresponsive. It happened in Auburn, about 45 miles west of Boston.

An autopsy was performed Sunday night on the toddler, who died shortly after being taken to the hospital. The second girl, also around 2 years old, remained in critical condition at a local hospital.

The district attorney says the foster mother has been cooperating with authorities.

No arrests have been made.