Investigators are trying to figure out what sparked a four alarm fire that quickly spread to two other buildings in Brooklyn late Sunday night.

Officials says the flames broke out just before 10:30 p.m. at a three-story building located at 49 Diamond Street in Greenpoint.

More than 140 firefighters responded to the scene.

"I saw like flickering lights, almost like firecrackers and then I smelled smoke and I was like well that's weird, so I went downstairs to see what it was and at that point I saw people covered in soot," said one witness.

Sources say two of the buildings have orders in for partial demolition.

Three people have been displaced.