Firefighters responded to reports of a man trapped in the basement of a Bergenline Avenue home in Union City just before 9:30 p.m. Wednesday.
They were quickly forced back by the heavy flames and were unable to search for the man. He was later found dead.
The flames quickly spread down the block, comprised of buildings with apartments and stores.
More than 40 residents fled the flames and were spending the night at a nearby school.
"It's a devastating fire on a very cold night for these families," Union City Mayor Brian Stack said. "Some of these families are very poor. They are just trying to make ends meet."
Up to 10 firefighters were treated for minor injuries, many of them slipping on the accumulating ice from fire hoses.
Bergenline Avenue and several other nearby streets were closed.
Residents said the block went up in flames in a similar blaze 11 years ago.
The cause of the current fire is under investigation.
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