One of the residents tells News 12-New Jersey she awoke to her landlord banging on her door as flames began to spread between the buildings at 1 and 3 Franklin Avenue in Harrison.
Fire Chief Thomas Dolaghan says the fire appeared to start near the top of one of the structures.
Eighteen families were evacuated from the four-story buildings and adjacent dwellings. There are no reports on injuries.
Police received the emergency call around 5:25 a.m. Monday.
Fire companies from at least six neighboring towns were on the scene.
The cause is under investigation.
