An investigation is ongoing on why a transformer failed causing a power outage in Southern Knox County.

Over 600 Duke Energy customers in the Monroe City and Wheatland areas were left without electricity from midnight until late afternoon.

Company officials announced at 5:30 p.m. that service had been restored using a mobile substation.

Duke Energy spokesperson Kurt Phegley explained that the outage was caused by an internal fault in the substation transformer bank.

“We conduct routine inspections on each of our substations to detect potential issues, but this transformer bank showed no signs of failure before the event,” Phegley said.

He added that further inspections are underway to determine whether the existing transformer bank can be repaired or if a replacement is necessary. The mobile substation will remain in service until until the problem is solved.