The incident occurred at the Appin West Colliery mine site at Douglas Park around 3am today.

The group were trapped in the rubble for more than 30 minutes.

Once freed, two workers were taken to Liverpool hospital, including one with serious head injuries.

The two other workers were taken to Wollongong Hospital for treatment.

GM3, which recently acquired the mine site, confirmed operations at Appin Mine have been paused and an investigation was under way.

“Emergency services responded promptly, and all appropriate emergency protocols were enacted,” a spokesperson said.

“An investigation is under way with the NSW Resources Regulator and other relevant authorities.

“Operations have been paused until further notice.

“At GM3, Our focus always remains on the safety of our people.”