Four members of one family — including a 4-month-old baby and a teenage girl — were killed, and a grandmother was injured after a fire possibly started by a discarded cigarette engulfed their New Jersey home.

Neighbors said three generations of the family were living in the split-level home on Buttonwood Drive in the Lanoka Harbor section of Lacey Township, where the blazing inferno ignited around 12:30 p.m. Tuesday.

“We heard screaming. I was like, ‘Oh my God, the kids are still in the house,'” neighbor Robert Juska told CBS New York.

Juska said he and another neighbor ran toward the burning house, jumped the fence and found the family’s grandmother hanging out the back window.

“She was coming out of the top window. She jumped down, but she snapped her leg,” Juska said.

Despite her injury, the elderly woman tried to get up to run back inside the house to save her grandchildren — but she passed out by the door, the neighbor said.

“So we picked her up and carried her out here and then she was telling us there were four more people in the house and I was like, ‘Who?’ And she was like, ‘the kids.'”

Another neighbor, speaking to News 12 New Jersey, said he busted an air conditioning unit out of a window and peered inside the house but could not climb in.

“There was so much stuff in the house. When I kicked the back door, it wouldn’t even open,” he said.

By the time firefighters arrived, the house was fully engulfed in flames.

First responders tried to rescue the four people still trapped inside the home — but then a large portion of the roof caved in, forcing all the crews to evacuate, Ocean County Prosecutor Bradley Billhimer said in a statement.

“This is an unspeakable tragedy, and our prayers are with the loved ones of these victims,” Billhimer said.

The prosecutor on Wednesday identified the victims who died in the fire as Jennifer Wright, 39, Alaina Wright, 34, a 14 year-old girl and a 4-month-old baby.

The grandmother who survived, identified as 67-year-old Brenda Wright, was taken to Community Medical Center to be treated for her injuries. She was listed in stable condition.

Investigators from multiple local and state agencies have determined that the inferno started on the porch, and that “improperly discarded smoking material cannot be eliminated as the cause of the fire.”

“The cause of the fire has been ruled accidental,” Billhimer said.