UPPER ST. CLAIR, Pa. (KDKA) – An unmarked underground mine void that might affect the stability of a road in Allegheny County has forced an unexpected closure.

Painters Run Road just west of its intersection with McMillan Road in Upper St. Clair closed Thursday, Allegheny County says.

READ MORE: Paperless Ticketing Leads To Long Lines Outside Heinz Field Ahead Of Steelers Game

Crews encountered an unmarked mine while completing drainage work there. According to the Trib, a worker fell about 5 feet into the ground but wasn’t hurt.

It’s now unclear how the mine is affecting the road’s stability, and until crews can make sure it’s safe, Public Works will keep that part of the road closed.

READ MORE: T.J. Watt Suffers Groin Injury, Won't Return To Sunday's Steelers Game

The county says representatives from the Pennsylvania DEP’s Bureau of Abandoned Mine Reclamation will come out to evaluate the mine void and potential remediation options.

Traffic will be detoured using Bower Hill, Kelso and Rob Hollow roads.

MORE NEWS: Pittsburgh Police Investigating Shooting In Homewood

While repairs to the bridge deck, installation of a guide rail and paving has just wrapped up on Painters Run Road, paving on other sections between Bower Hill Road in Scott Township and Cedar Boulevard in Mt. Lebanon will begin tomorrow.