According to the Newscatle Herald, an unknown caller contacted the mine offices, saying there was a bomb located near the site’s administration and workshop areas.
It took several hours for police and emergency services to clear the area and declare the bomb threat a hoax. Work resumed at the mine shortly after.
The incident comes on the heels of jobs reductions announced last week, which affected about 50 contractors.
Big miners Glencore Xstrata (LON:GLEN) and Vale (NYSE:VALE) have also decided to mothball Upper Hunter mines in coming months.
Anglo American (LON:AAL), meanwhile, said it is cutting contractors at its Drayton thermal coal mine, slated to run out of fossil fuel reserves in 2017, and putting permanents on a five day roster.