Crews cleaning up an oil spill believed to contain PCBs are expected to work through Monday to mop up the sludge, Tooele Army Depot officials said Saturday.

"We're working on the worst-case scenario. And we have completed the majority of the cleanup process," Depot spokeswoman Susan Broadbent said. "We're in the final stages."Results from samples taken to determine the level of polychlorinated biphenyls in the oil won't be released before Monday, said Broadbent.

Lightning or a short circuit damaged a wooden power pole that caused a transformer in the base's north area to fall about 1:30 p.m. Thursday. Some 16 gallons of oil spilled onto the dirt.