One of the United States’s largest oil refineries was set ablaze after a reported explosion, prompting a shelter-in-place order in Port Arthur, Texas.

Port Arthur’s Police Department website featured a notification ordering residents in the area west of Stilwell Boulevard, south of Highway 73, Sabine Pass, and Pleasure Island to shelter in place until the all-clear was given. Despite the plant’s sensitivity, Sheriff Zena Stephens said the explosion was likely caused by an industrial heater, KFDM reported.