Emergency services were called to the mine at 11.15pm after a 26-year-old man became trapped in a pipe after attempting to dislodge debris.

Paramedics attempted to revive the man, who was in cardiac arrest, and continued treatment while he was transported to Cobar Hospital.

The worker was announced deceased after arriving at hospital.

"I would like to extend my deepest condolences and prayers to the man's family, friends, co-workers and the wider Cobar community, during this very difficult time," NSW resources and energy minister Anthony Roberts said this morning.

Police attached to the Darling River Local Area Command have launched an investigation into the incident, and mine investigators and Work Cover are also assisting.

NSW Police will prepare a report for the Coroner.

The accident is not the only fatality reported at the CSA mine, with another worker dying in an accident last year underground.

The mine is operated by Cobar Management, and focuses on mining copper with a silver co-product.

It produces over 1.1 million tonnes of ore and more than 185,000t of copper concentrate per annum.

The accident marks the fourth mining death in NSW this year, with a worker killed at Idemitsu's Boggabri coal mine in the Gunnedah Basin last month.

Two mine workers also died at Yancoal's Austar underground mine in April when walls collapsed in a development tunnel.