The items, including stone tools, were scattered along a track that was cleared by a grader on January 10.

The mine notified the Department of Planning of the incident on March 10.

The department's investigation found that the contractor operating the grader had not been told about the artefacts.

It also found that the mine had not implemented its Aboriginal Cultural Heritage Management Plan, as required by its consent conditions.

Following consultation with a local Aboriginal community, the mine has agreed to fence around the disturbed artefacts and other areas known to contain artefacts. It is also updating its ground disturbance procedures and will provide additional training.

The mine is also liaising with the local Aboriginal community about plans to create a visitor display site for artefacts salvaged from the site, including the disturbed area.

Xstrata Coal could not be contacted for comment about the incident yesterday.

The Department of Planning also investigated fumes from a blast at Coal & Allied's Hunter Valley Operations mine on March 15 that resulted in five community complaints.

The department found that while there was no specific breach of the mine's consent conditions, it has directed the mine to revise its blast monitoring program.

It must now use comprehensive controls to minimise emissions, including fumes.

The department's Singleton office received 12 complaints about mining compliance-related issues in April.