DUXBURY, Massachusetts (AP) — A 32-year-old mother in Massachusetts is expected to be charged in the killing of her two children and the injuring of her infant son, Plymouth District Attorney Timothy Cruz said Wednesday.

Authorities arrived at a house in Duxbury Tuesday night after receiving reports of a woman jumped out of a window. They found her and the children unconscious with obvious signs of trauma. The mother, Lindsay Clancy, remains hospitalised and will be arraigned on homicide charges after she is released, Cruz said. It appears the children were strangled, he added.

"This is an unimaginable, senseless tragedy, and it is an ongoing investigation," Cruz said at a news conference Tuesday near the scene in Duxbury, a coastal town about 30 miles (48 kilometres) south of Boston.

Police and firefighters responded to the home just after getting a 911 call from a male resident who reported the woman jumped out the window, Cruz said. A five-year-old girl, Dora Clancy, and her three-year-old brother, Dawson Clancy, were pronounced dead at a hospital, he said. A seven-month-old boy was flown to a Boston hospital for treatment.

Lindsay Clancy is a labor and delivery nurse at Massachusetts General Hospital, according to The Boston Globe.

"We are shocked and saddened to learn of this unthinkable tragedy," the hospital said in a statement provided by Michael Morrison, the senior director of external communications. "We extend our deepest sympathies to all those affected by these devastating events."

In Duxbury, the Reverend Bill Ferguson from the Pilgrim Church told Boston 25 television station that eight churches had opened their doors in the wake of the tragedy.

"It is hitting hard. If you are a parent of a young child, even if you are not, when children are involved especially --- There is a special numbness that comes in with that," Ferguson said.