The wall collapse just a few days after two earthquakes hit the area, located about 20 kilometres south of Orange.

The wall breach was noticed in the late afternoon on Friday when workers noticed a section of the northern dam wall had collapsed into the southern tailings dam.

The tailings dams contain byproducts of mining and can contain materials which are harmful to the environment and human health.

The dams are generally constructed using earth-fill and gradually raised over time.

The Cadia mine is owned by Newcrest, one of the largest gold mining companies in the world.

Newcrest were unable to confirm whether the recent earthquakes had contributed to the dam’s wall failure but said it was conducting a thorough investigation.

The company said operations at the site had been suspended pending the investigation and that the break had posed no safety threat to workers.

But National Secretary of the Australian Workers Union, Daniel Walton said that many of the workers on the site still don't feel safe given the recent earthquakes.

"A lot of workers are worried that the mine is not taking this activity seriously enough and they do have concerns about safety," he said.

Local landholders were notified along with the relevant authorities.

In a statement, Newcrest said that safety was its highest priority as it worked to assess the impact of the wall break.

“The Cadia tailings dams have been regularly inspected, reviewed and monitored; and have been fully certified to industry standards by independent third parties.

“As a precaution Newcrest stopped depositing tailings into both dams on 9 March. Operations were subsequently progressively suspended pending further investigation.

“We are monitoring the impact carefully, and have observed no environmental damage. We believe there is no threat to personal safety.”

On Thursday, two earthquakes were recorded in the area, ten seconds apart and just over two kilometres from the mine.

The earthquake had a magnitude of 2.7 and was reportedly felt in the area.

Last year, the Cadia mine was evacuated after an earthquake with a magnitude of 4.3 was registered near the site.

The site remained closed for several months leading to a 48 per cent drop in profits for mine’s owner Newcrest.

In a statement, the NSW Environmental Protection Agency said it was aware of the collapse and was inspecting the site.

They also said they understood that the tailing had been contained.