The building, managed by Newark Housing Authority, was all but destroyed around 6 p.m. after the explosion rocked the building.
The cause of the blast is still under investigation.
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The walls of the building were completely blown off, leaving behind debris and forgotten furniture.
Valery Lasky and her son work at a nearby deli and witnessed parts of the event.
"He said 'Ma, a building exploded.' I ran and looked and saw a guy climbing down the rubble. The owner of the store said there were people all over the ground," Lasky recalled.
Officials in Newark say six people were injured in the blast.
Five people were taken to area hospitals, and one woman suffered from serious burns.
Several injured, building decimated in Newark explosion
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"I actually know the man who is in there. His name is Mario, and I just hope he is going to be OK," Lasky added.
The Red Cross is assisting at least 31 displaced families, including 28 adults and three children, as investigators try to pin down what happened.
"No, we don't have any information about where the explosion started, what unit it started from, this is an ongoing investigation," said Newark Public Safety Director Fritz Frage.