Two Paterson firefighters and a K-9 went in once it was deemed safe to search three hours after the middle of the five-story building near the corner of Williams Street and Arlington Avenue gave way around 5 p.m.
The building had been under construction and there was no reason to believe anyone was inside, city officials said.
Responders included members of the Urban Area Security Initiative (UASI), which includes firefighters from Hackensack, Paterson, North Hudson Regional Rescue, Bayonne, Elizabeth, Hoboken, Jersey City, Newark, Paterson, and Morristown, as well as NJ Transit and Port Authority police.
Several of them formed bucket-brigade-type lines to remove pieces of rubble.
Three neighboring buildings were evacuated as a precaution. NJ Transit provided warming stations.
Authorities said it was too soon to determine what happened.
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