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By Erwin Seba and Ashitha Shivaprasad

HOUSTON, May 8 (Reuters) - A heater on a reformer at PBF Energy's PBF.N 190,000 barrel-per-day Chalmette, Louisiana refinery exploded on Friday, setting off a fire, said two people familiar with plant operations.

No injuries were reported following the explosion in the 17,500-bpd reformer, the sources said.

Video of the blast posted on social media showed the explosion beginning at the top of the reformer. A huge column of flames and black smoke then quickly followed with the smoke plume rising high in the air above the refinery.

The explosion occurred at 12:51 p.m. CDT (1751 GMT) and refinery personnel began battling the ensuing fire, according to a message posted by the Chalmette refinery.

"Fence-line monitoring confirms no off-site impacts," according to the message from the refinery. "Everyone working in the area is safe and accounted for."

The St. Bernard Parish government posted a notice saying the fire on the reformer had been contained by about 2:30 p.m. CDT (1930 GMT).

Reformers convert refining by-products into octane-boosting components that are added to unfinished gasoline to make premium and mid-grade blends of the fuel.

The sources said the heater was located at the top of the reformer.