Workers at Burgas-based Cherno More-Burgas mine have spent more than 30 hours in the pit in protest over unpaid salaries.

Forty people refused to leave as their night shifts ended on Thursday morning, with 20 colleagues willing to join them in the afternoon.

The 62 workers located 300 meters underground are now determined not to come out before receiving payment for the last two months, the Bulgarian National Radio reports.

They have reiterated they are overhead in debt and insist institutions have repeteadly turned a blind eye to their needs.

"We could have to take corpses out in a few hours, but there is no-one to pay us any attention".

Doctors and mine officials say risk is posed to ther health due to the artificial ventilation.

One of them has been forced out due to high blood pressure.

Miners are venting their anger at the National Electric Company (NEK), which is to transfer money to Sliven's heating utility, Toplofikatsiya Sliven, which has to transfer funds to the Cherno More mine.

Economy Minister Vasil Shtonov has commented on the strikes, saying the heating utility in Sliven has been allocated enough money from NEK and is able to comply with workers' demands.

Shtonov, however, has stressed both are private entities.