A deadly fire tore through a building that housed Guatemalan immigrants, partially collapsing the roof and killing at least five people Saturday, and it may have been intentionally set, a fire official said.

The early morning blaze at the Brooklyn building is being investigated as a possible case of arson because it started behind the door of the first-floor entrance to the building, New York City Fire Commissioner Salvatore Cassano said.

"That's not where a fire would normally start," Cassano said after surveying the devastation of the fire, which trapped residents and caused the interior walls to collapse. "That's why this is a fire that we are saying is very likely to be incendiary."

Four people in the building were injured, including an infant and a child who were tossed out the window by a woman frantically trying to save them. The infant was in critical condition with a fractured skull after bystanders below failed to catch him, officials and witnesses said. The other child landed on an awning.

At least one adult was hospitalized, and 13 firefighters were injured, none of them seriously, officials said.

The fire started at about 2:30 a.m. and flames quickly engulfed the three-story building on a busy commercial strip, consuming a ground-floor Japanese restaurant and two apartments on the upper floors. The stairwell between the floors collapsed, as well as part of the roof, trapping residents, according to fire officials.

As the fire raged, a woman held a baby boy out a third-floor window. Bars covered the lower half of the window, keeping the woman from climbing out, neighbor Juan Gabriel told The New York Times.

"She was screaming, 'Help me, help me,' " Gabriel said. Moments later, she threw the infant out the window to Gabriel and two other men.

In the darkness, the child fell to the ground, authorities said. She then tossed another child out the window. He landed on the awning below.

It wasn't immediately clear whether the woman survived the fire.

Alex Lazaro, a Mexican man who works as a union organizer and lives in the neighborhood, said that the people who lived in the building were poor immigrants.

"They live very humbly and don't make enough to live in a better place," Lazaro said, standing on a sidewalk looking at the burned-out shell of the building, which was cordoned off.

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