A power failure at the 90-Thousand-barrel-a-day Suncor oil refinery near Denver is reducing production at the plant, which produces 35 percent of Colorado's gasoline and diesel, the company says.
A company news release says the power interruption happened about 9 a.m. Sunday morning.
The fluctuation shut down the west side of the plant, which converts so-called "sour crude" into finished petroleum products.
The east side of the plant remains operational.
According to Canada-based Suncor, the plant in the Denver suburb of Commerce City, produces gasoline, diesel, jet fuel and asphalt.
The company says it notified the Colorado Department of Health and Environment and is investigating the cause of the power failure.