A fire that raced through a three-story row house early Tuesday, killing five children, may have been caused by the youngsters playing with matches, authorities said.

Police said they are trying to confirm whether the children were alone or in the care of a teenage baby sitter.

Authorities interviewed the two mothers of the dead children, and police said they don't know where the mothers were at the time of the fire.

"There's an unsubstantiated report that (one of the mothers) left the children in the custody of a 17-year-old female," Police Chief Nate Harper said.

Flames were shooting from all three floors of the wood-frame building when firefighters arrived, officials said. The children, who ranged in age from 3 to 7, were found on the second floor, where the fire apparently started, authorities said.

Police said they were trying to figure out if the baby sitter does exist. Authorities said the girl was apparently part of a neighborhood group of youngsters known as "the crew."

"The community really seems to be outraged by this fire — five children left alone in the house ... but we really need to identify the babysitter if the babysitter does exist," Pittsburgh police Cmdr. Maurita Bryant said.

Bryant said "charges will be filed once we complete our investigation." She declined to elaborate.

Police refused to release the mothers' names.

"Until we find out otherwise, the mothers are victims. I am sure they are traumatized by the loss of their children," Bryant said.

The fire broke out at about 1:30 a.m. in the city's Lincoln-Larimer neighborhood. A neighbor called authorities after smelling smoke and coming out of her house to see two 8-year-old boys yelling for help. Screams were coming from inside the smoky rowhouse.

"They were screaming, and five minutes later they stopped screaming," neighbor Sontaya Perry, 22, said. She said she tried to get in the house but the wooden stairs leading to the door were on fire.

The dead were identified as Cedano Holyfield, 4; Daekia Holyfield, 7; Dezekiah Holyfield, 3; Andre Rankin, 6; and Azquel Rankin, 5. The Holyfield children lived in the home and the Rankin children lived in the Hazelwood neighborhood.

All five children died from smoke inhalation and carbon monoxide poisoning, the medical examiner said.

Steve Pilarski, manager of administration at the Allegheny County medical examiner's office, said all the children were related, but he couldn't provide details.

The two 8-year-olds, whose names were not released, did not need medical treatment. It was not immediately clear where they lived.

The fire gutted the row house and spread to a vacant building next door. Investigators were at the blackened house throughout the day Tuesday, examining charred rubble and removing debris.

A white plastic table and chairs sat on the home's porch, next to a child's bicycle and wagon. A toy lawn mower sat next to the front stoop.

City officials said both houses will have to be torn down.