Tesoro Co. officials said Thursday it would be a couple of days before they will be able to determine what caused a three-alarm fire Wednesday at their Salt Lake refinery.

The fire started just after 9 p.m. at a flare stack at the refinery, at 900 N. 600 West. There had been a power outage in the area earlier Wednesday. Just after the power was restored, a fire ignited as crews were restarting the refinery.

Salt Lake fire spokesman Mark Bednarik said crude oil that had leaked and was at the base of the flare stack ignited. What caused the oil to leak was still being investigated.

Huge flames lit up the night sky and could be seen across the valley. Emergency crews temporarily shut down I-15, and Beck Street and FrontRunner trains were temporarily shut down as a precaution.

No one was injured. Maintenance equipment, including a trailer that officials described as being in the wrong place at the wrong time, was consumed by the flames and destroyed.

The refinery was still producing its regular output of product Thursday, thanks to reserve supplies, said Tesoro Senior Vice President Lynn Westfall. The refinery will be operating with its stored supplies for a couple of days and then should return to normal procedures, he said.

"The damages appear to be minimal," he said.

Tesoro's fire brigade took the lead in extinguishing the fire, using a foam-based material for suppression.

— Pat Reavy