But they say the blaze that destroyed the three-story building in Passaic on Friday afternoon isn't considered suspicious.
One resident, identified only as a 53-year-old woman, remained in critical but stable condition Saturday at St. Joseph's Regional Medical Center, while two other residents rescued by firefighters were treated there Friday for minor injuries and later released.
Two firefighters - one who dislocated his shoulder and another who may have broken one or more ribs - were also taken there for treatment.
Officials say the fire was reported around 4 p.m. Friday and burned for several hours. About 80 residents were displaced by the blaze.