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By Nicole Jao and Ashitha Shivaprasad

NEW YORK, June 25 (Reuters) - A fire broke out at Monroe Energy's 190,000-barrel-per-day refinery in Trainer, Pennsylvania, on Thursday, the company said.

The fire occurred in a process unit pump room on Thursday morning, the company said, adding that an on-site fire response team and emergency response resources were deployed.

"We are taking all necessary steps to extinguish the fire," Monroe Energy said in a statement.

The company said the cause of the incident would be investigated.

The fire occurred while the refinery was restarting the 68,000-bpd fluid catalytic cracker after an outage last week, a source familiar with the matter said. A catalytic cracker converts heavy crude oil feedstock into petroleum products.

The Trainer refinery, located southwest of Philadelphia, is owned by Monroe Energy, a subsidiary of Delta Air Lines DAL.N. The plant produces jet fuel and other transportation fuels including gasoline and diesel.

Delta did not immediately respond to a Reuters request for comment.

U.S. jet fuel prices jumped after the start of the U.S.-Israeli war on Iran, as attacks disrupted crude and fuel exports from the Middle East. Prices are now set to ease as crude prices fall and more oil tankers begin moving through the Strait of Hormuz. However, any further disruptions could tighten the already constrained fuel market and push prices higher again.