Phillips 66 (PSX) on Friday said a rainstorm caused an operational disruption and above-normal gas emissions at its Sweeny refinery in Texas.

"Heavy rain storm event caused a process upset," the refinery said in a statement to the Texas Commission on Environmental Quality. "Operations personnel brought the unit back to a safe and normal state as soon as possible."

It said the emissions happened Thursday evening and included the release of some 3,600 pounds of sulfur dioxide.

The 247,000 barrel-a-day Sweeny refinery is located in Old Ocean, southwest of Houston.

Write to Dan Molinski at dan.molinski@wsj.com