(CNN) -- A fire that spread across several row houses in Harrisburg, Pennsylvania, claimed the lives of four children and an adult Monday night.
Investigators believe the fire started from a space heater in the downstairs living room of a row house, according to Chuck Ardo, spokesman for Harrisburg Mayor Linda Thompson.
There was a "chill in the air" when the fire broke out around 7:30 p.m. and it was "clearly cold enough that you need to keep small children warm," Ardo said.
The four deceased children were 2 to 4 years old, and the fifth fatality was a 48-year-old woman, he said.
The victims were in the same house, but several houses caught fire.
Ardo said firefighters were grief-stricken by the tragedy.
"First responders were just absolutely devastated," he said. "There were firemen standing there crying in the street."
Officials had not identified the victims and would not say whether they were related.
Ardo said he was not aware of any other injuries.