A fire burned for more than six hours at the Sinclair Oil refinery in south-central Wyoming.
Officials with Salt Lake City-based Sinclair say nobody was hurt.
The fire started around 3:30 a.m. Friday in the plant's alkylation unit. The refinery's fire department extinguished the flames around 10 a.m.
The company said in a release it had notified Wyoming workplace safety regulators and begun an investigation. The refinery continued to operate at normal rates.
In 2012, three fires injured seven workers at the refinery in the town of Sinclair.
In October, the Wyoming state workplace safety office announced more than $700,000 in fines against Sinclair for 22 alleged workplace safety violations. Problems that led to the fines included a toxic gas release that sickened 22 workers in May.