A steam pipe explosion in the Flatiron District sent thick clouds of steam into the sky and left a crater in the middle of a Manhattan Street.
Most of the businesses in the neighborhood were shut down as investigators cleared traffic.
Con Edison said it was testing for asbestos and other airborne contaminants in connection to the steam. The agency informed local media that it expected positive test results, meaning decontamination in the area could take several days.
At least four people suffered minor injuries in the blast, which rang out at about 6:30 a.m. near Fifth Avenue and 21st Street, reports say.
Hours later steam was still billowing into the street as crews investigated the source of the blast.
NBC New York reports people were seen with masks over their faces on Sixth Avenue.
Local doorman Patrick Tentes tells NBC he was working the overnight shift when he noticed the back room of his building was inordinately humid. He checked the basement and found it even hotter.
He recalled seeing the explosion light up the street early in the morning.
"There was a bunch of mud spraying the door, it didn't seem stable," he told NBC. "I was scared."
The steam at first looked like smoke and many locals suspected a terror attack.
NBC points out that Thursday morning's blast comes 11 years to the day of another steam pipe explosion near Grand Central station, which blew debris dozens of stories into the air.
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