A Marathon Petroleum worker has died from injuries suffered in a fire that broke out on May 15 at the company's giant Galveston Bay Refinery in Texas City, Texas, the company said.

The fire broke out at about 9:30 a.m., the company said.

"A Marathon employee has passed away as a result of the fire today at Marathon Petroleum's Galveston Bay refinery," company spokesperson Jamal Kheiry said in an emailed response to Reuters.

The fire has been extinguished and the cause of the fire is under investigation, Kheiry said.

Two people familiar with the matter said the fire broke out when workers were doing routine maintenance and a seal failed on the 75,000 bbl/d Ultraformer 3 (UU-3).

UU-3 is the bigger of two reformers at the 593,000-bbl/d refinery, which is the second largest in the United States, according to the U.S. Energy Information Administration. Reformers convert refining byproducts into octane-boosting components added to gasoline.

"Emergency responders are on the scene, and all employees and contractors are being accounted for currently," the company said in a statement, adding that Marathon had made all regulatory notifications.

The Texas City Emergency Management Department said on Twitter earlier that a shelter-in-place order was not needed.

A contract worker died in March after receiving an electric shock at the refinery.

Texas City is located 42 miles (68 km) southeast of Houston.