NEW YORK - Two sibling toddlers died Wednesday after suffering steam burns in a New York City apartment, and investigators are looking into whether a radiator malfunctioned, authorities said.

"Our city is mourning the loss of two young children in a tragedy earlier today that appears to be connected to a steam radiator in their family's Bronx apartment," Mayor Bill de Blasio said in a statement.

Firefighters who rushed to the building, which housed several homeless families, were met in the lobby by the victim's father with the unconscious girls, New York Fire Department spokesman Jim Long said.

The firefighters immediately performed CPR on the toddlers, Long said.

The girls, identified as Scylee Vayoh Ambrose, 1, and Ibanez Ambrose, 2, were taken to a hospital where they were pronounced dead Wednesday afternoon.

"I saw the firemen carry them out," neighbour Eddie Perez, 68, told the Daily News. "They didn't look like they were alive. They were limp."

"Our law enforcement, buildings, fire and social services personnel will not rest until we can answer what has given rise to this heartbreaking incident," de Blasio said.

The medical examiner will determine what caused their deaths. However, fire officials said both children had severe burns apparently caused by a steam leak from a malfunctioning radiator.

"It appeared to be a failure of the radiator," said Long. "A valve or release valve that became separated."

A neighbour told WABC-TV that she heard a woman screaming and saw steam emerging from the closed door.

"We are devastated by this tragedy," said Department of Social Services Commissioner Steven Banks. "We are investigating and taking steps to immediately transfer the four other families being sheltered at this location to another shelter."

A spokesman for the city's Department of Buildings said investigators were at the scene. A telephone call to the operator of the shelter was not answered.

"We will certainly be looking at Building Department records, previous complaints, outstanding complaints, current complaints," FDNY Chief Michael Gala said.

News from © The Associated Press, 2016