JEANNETTE — Investigators were searching Thursday for the cause of a fire that tore through a house in the Pittsburgh suburbs, killing a man and four children and spreading to another house before the flames were extinguished.

Firefighters arrived quickly but found the two-story house in Jeannette already engulfed. The man's fiancée and two other children were rescued by a neighbor, police and firefighters.

Neighbor Jack Mull said he saw the flames when he stepped outside to have a cigarette early Wednesday, just after midnight. He screamed at his daughter to call 911 and raced to get a ladder. He told reporters he saw the children's mother, Miranda John, standing on a rear roof with a small child.

“The mother, she just didn’t want to give up,” said Mull, adding she tried to go back inside. “It’s the worst thing you could ever imagine, knowing they were in there.”

Miranda John and the surviving children, ages 10 and 1, were hospitalized.

The Westmoreland County coroner identified the victims as Tyler J. King, 27; Kyson John, 7; Kinzleigh John, 6; Keagan John, 3; and 1-month-old Korbyn John. The coroner’s office said a ruling on the cause and manner of death was pending further investigation. Autopsies were performed.

“It’s a devastating loss for our families,” said Delena Lewis, Tyler King’s mother. “Not only mine, but his fiancée and the other two surviving children. They’re left without a father. How do you explain that to them?”

Jeannette Fire Chief Bill Frye said a nearby hydrant didn't supply enough water to fight the raging blaze, and additional tanker trucks had to be called in.

“That’s when we were able to get sufficient water to bring the fire under control,” he said. “By the point we got water, the main house was already collapsing.”

The fire spread to the house next door, but everyone there evacuated without injury.

A prayer vigil was held outside City Hall later Wednesday.