Workers were directed to tip their loads and move to their nearest emergency assembly points about 1am after a Mount Arthur employee received a bomb threat by phone.

A caller alleged there was a bomb in the administration area or nearby workshop.

More than 100 workers spent several hours in crib sheds on the mine site as police and emergency services responded to the threat.

Work resumed on site after staff were advised the threat was a hoax.

In a statement yesterday BHP Billiton confirmed it had ‘‘suspended operations and evacuated employees as a precautionary measure due to information being received’’ at its Mount Arthur site.

‘‘Police were notified and the information assessed. Mount Arthur Coal has recommenced operations having deemed it safe to do so,’’ the statement said.

NSW Police media confirmed there was a ‘‘police operation [but] our general policy is not to make further comment about this type of incident’’.

Last week about 50 Mount Arthur contract staff were put off without warning as mine workers and BHP Billiton negotiate a new enterprise agreement.

The Newcastle Herald has been told workers were warned another 50 staff from the workshop, maintenance area and coal plant might be laid off in the near future.