BAYTOWN, Texas A fire broke out late Wednesday at Exxon Mobil Corp's (XOM.N) refining and chemical complex in Baytown, Texas, the largest operating U.S. refinery, Exxon Mobil said.
The fire at the 560,500 barrel per day (bpd) refinery east of Houston was under control and remaining plant operations were not affected, Exxon said. There were no reported injuries.
According to sources familiar with refinery operations, the fire broke out at the diesel hydrotreating unit, which uses hydrogen to remove sulfur from motor fuel.
Exxon did not specify the exact location of the fire, which was reported at about 5:00 pm local time (2200 GMT), disclosing that it was confined to a refinery process unit.
"Remaining plant operations were not impacted from the event," said Exxon spokeswoman Rachael Moore in a statement.
A hole in a reactor caused the fire and triggered flaring at the complex, a filing with the U.S. National Response Center (NRC) showed. It did not identify the unit involved.
Exxon said emergency response teams had the fire under control at the five-square-mile (13 square km) complex, one of the world's biggest refining and petrochemical plants.
Video from local television station KRTK earlier showed flames high up on a column at the complex.
Exxon said it will investigate the cause of the blaze and the president of the refinery workers union said they were ready to join the probe.
"Nobody was hurt, that's the good thing," said Ricky Brooks, of the United Steelworkers union. "We're looking forward to working with the company to find the cause."
About two hours after the fire broke out, a large firefighting apparatus could be seen spraying water on the blaze, creating a cloud of steam and smoke in the middle of the maze of pipes and columns at the heart of the refinery, according to a Reuters eyewitness.
The fire appeared to damage the side of the unit in the images broadcast on television.
A hydrotreater is not a main production unit at a refinery. The loss of a diesel hydrotreater could lead to reduced diesel production, but would not impact wide-scale plant operations.
(For refinery outages in the Reuters Oil Fundamentals Database see here or go to)