Tesoro refinery in Mandan

The Mandan refinery, shown here in 2016, began operations in 1954 and has a capacity of 71,000 barrels of oil per day, according to its company website. The facility manufactures gasoline, diesel fuel, jet fuel, heavy fuel oils and liquefied petroleum gas. Refined products are trucked and railed from Mandan and also shipped east via pipeline to supply the Jamestown area, eastern North Dakota and Minnesota.

A gas leak at the Marathon Petroleum Mandan Refinery on Thursday morning prompted an evacuation of non-essential employees, said spokesman Ron Day.

Operators detected a pinhole leak in a process unit about 10:40 a.m. that released a gas that Day described as a propane-type material.

All non-essential personnel from the refinery reported to a safe muster point until the all-clear was given shortly after 11 a.m., Day said.

Operators shut down and depressurized the unit, which will be repaired. There were no injuries or exposures from the incident, Day said.

The North Dakota Department of Health and local law enforcement were notified.

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