A house fire that officials said might have simmered undetected for hours Saturday killed five people, including a 7-month-old baby and her mother.

Firefighters found the victims unconscious and severely burned on the second floor of a single-family house in a residential neighborhood, Warwick Fire Chief Kevin Sullivan said. They were called to the house just before noon by a man who was sleeping on the first floor after a late-night party, he said.

"I've never seen a fire with this many fatalities," Sullivan said. "We just kept pulling people out one after the other. It was a very gruesome scene to see those people come out."

The man who called 911 went to bed at around 3 a.m. and woke up at about 7 a.m., and nothing was wrong, authorities said. But he was awakened again several hours later when a section of the first-floor ceiling collapsed, Sullivan said.

The man, whom authorities didn't identify, tried to run up to the second floor but was turned away by intense smoke and heat.

State Fire Marshal Jack Chartier said the blaze likely started in a gap between the first and second floor, or a gap in the second floor ceiling, and burned slowly.

"This may have been smoldering silently after these folks went to bed," Chartier said.

The victims included 21-year-old Amanda Villeneuve and her daughter, Annabelle, who both lived at the house, which was owned by her father, James Weeden.

Weeden is the warden at the state's maximum-security prison. He and his wife were away in Vermont at the time of the fire Saturday.

Two other victims were identified as 20-year-old Dan Janik of Woonsocket and 24-year-old Nicholas Jillson of North Smithfield. The name of a 20-year-old woman who was killed hasn't been released.

Authorities said the fire was not suspicious, but declined to release its cause.