The fire killed two men who were trapped on the top floor of the building in Bushwick.
One of them died after jumping out the window.
Investigators say the fire began on the floor below where occupants tried to put it out themselves delaying their call to 911.
They also failed to close their apartment door, so the flames spread quickly.
"I saw black smoke coming out the roof towards me. I opened the door and that's when I saw the smoke everywhere. The fire going everywhere in the room," neighbor Bernard Downes said.
The FDNY says there are no signs the building was illegally subdivided, despite complaints last fall that went uninvestigated.
City Council Speaker Christine Quinn has set a hearing for next month to look into the problem of inspectors not getting access.