WHITING, Ind. (AP) — Four workers have been injured in an industrial accident at northwestern Indiana’s sprawling BP Whiting Refinery.

The (Northwest Indiana) Times reports the workers were injured Friday and taken by ambulance to local hospitals.

BP spokesman Michael Adbendhoff said the workers’ conditions were not immediately known.

The company said in a statement that the workers were injured in “an incident” at a refinery’s power distribution center but provided no additional details.

Whiting Mayor Joe Stahura says the refinery responded to the accident internally with its own in-house fire department, which is not uncommon.

The BP Whiting Refinery employs more than 1,800 workers. The complex converts crude oil from Canada and the Dakotas into gasoline that’s sold in seven states across the Midwest. It’s the largest refinery in the Midwest.