Southeast winds of 10 to 20 mph were impeding firefighting efforts, and authorities evacuated six blocks to the north of the scene, the (Newark) Star-Ledger reported Thursday.
The fire began in an ice cream store at about 2:30 p.m. EDT.
Firefighters were pulled back 2 hours later because of the intensity of the flames, officials told the newspaper.
"We've got everyone in the county coming," Seaside Heights Police Chief Thomas Boyd said. "We're in trouble here. We've got major problems."
New Jersey Gov. Chris Christie reached the scene at about 6:30 p.m.
"It's a desperate situation here," NBC News quoted Christie as saying.