"Really, really sad:" Girls ages 1, 2 killed in explosion in NYC apartment, possibly caused by radiator

NEW YORK --  Two young children were killed in an explosion in their apartment in New York City. Some are now wondering whether this tragedy could have been prevented.

The girls, ages one and two, died inside the building in the Bronx they called home.

"It's sad. It's really, really sad," Maritza Morales, a neighbor said. "My son called me that there was an explosion, and when he came down, my neighbor came running out with his two babies and that they were burned all over."

It's got me really shaken up," Gilberto Lorenzo said.

Lorenzo said he heard a 'boom' from a first-floor apartment, and he called 911.

Firefighters said there was steam coming from the apartment and it was starting to fill the hallway.

"Probably you're look at a radiator -- steam conditions from a radiator," Michael Gala, deputy assistant chief at FDNY.

The apartment building at 720 Hunts Point Avenue in the Bronx is considered a homeless cluster shelter. It's a privately-owned building that contracts with the city.

Housing experts are now wondering whether this tragedy could've been prevented.

"In 20 years of being involved in homeless issues I have never heard of something more horrific than this. This is horrible," Robert Mascali, a former NYC homeless services official said.

Most recently, neighbors said there have been problems with the heat.

The company that runs the building that houses the cluster shelter hasn't commented on this tragedy.