The fire broke out at around 2:30 Labor Day morning at the corner of Carroll Street and Kingston Avenue.
Eight firefighters were taken to the hospital for treatment, one with serious burns. He was taken to New York Hospital.
Many residents ran from the building, but a dozen had to be rescued. They were treated at the scene.
Officials say the fire is suspicious because of how quickly it spread.
The flames started on the second floor, where some construction had been taking place. It's not known if that played a role in the fire.
The fire was declared under control shortly before 5:00 a.m.
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