Queensland miners have taken spontaneous strike action for the second time in two days following the return of black lung disease.
Workers at Oaky Creek coal complex in central Queensland walked off the job on Thursday, just a day after miners at Grasstree mine, north of Emerald, walked out.
Mining union CFMEU said confirmation of three new cases of black lung disease in Queensland, three decades after it was supposedly eradicated, has sent shockwaves through the coal industry this week.
But it feared workers' health fears were not being taken seriously by Oaky Creek owner Glencore, which it claimed had forced casual contract workers back down the mine.
"After what we've learnt this week about black lung, forcing workers back down underground against their wishes shows a stunning disregard for Australian employees' health and safety," Queensland district president Stephen Smyth said.
"It is completely understandable that workers have concerns about their health and safety under the circumstances, and companies who try to ignore or duck the issue should be condemned."
The disease, caused by long-term exposure to fine, airborne coal dust in areas with poor ventilation, was thought to have been wiped out in Australia by the early 1980s.
The union expects more cases of the disease to be confirmed in the coming months and similar spontaneous action to be taken by Queensland miners.
Miners at Grasstree Mine are talking to owner Anglo American over their fears and have returned to work.
In a statement, Glencore said the health and safety of their workforce remained the company's top priority.
"None of the reported cases of pneumoconiosis (black lung) involve Glencore's underground coal operations in Queensland, nor have any of our employees who have stopped work over this issue been threatened with the risk of losing their jobs," it said.