Co-owner Boich spokesperson Mike Dawson told the Billings Gazette that 45 workers were ordered to the surface Thursday afternoon after gas readings in a previously mined and sealed tunnel at the operation near Roundup showed 125 parts per million.
He added that the impacted area is about 1.7 miles from the active working areas, and levels are normal in those locations.
All impacted miners at the 300 worker Signal Peak will remain on site while the issue is resolved and will work at the surface until regular operations resume.
Signal Peak and its operating subsidiary, Bull Mountain, is owned by Boich and First Energy as well as the Gunvor Group.
ILN is awaiting further word from federal officials on the mine’s conditions and status, and will report any updated information as it becomes available.