Workers of the Burgas-based Mina Cherno More Burgas EAD (Cherno More Mine EAD) are staging an underground strike over unpaid salaries for two months.
The miners who were supposed to end their night shift at 7 am on Thursday remained underground, according to reports of the Bulgarian National Television (BNT).
Some 45 miners are now staying 300 meters below ground, according to BNT.
The trade unions at the mine have secured rescue teams, ambulances and food supplies in order to prevent accidents.
It is still unclear whether the miners working the morning and daily shift will join their colleagues in the underground strike or stage a protest above ground.
Over the past two days, the miners at the Burgas-based mine have organized 1-hour protests at the beginning of each shift.
The management of the Cherno More Mine, as cited by dnevnik.bg, informed several days ago that it owed around BGN 600 000 for salaries for July and August to around 400 miners.