South Africa’s National Union of Mineworkers (NUM) said on Friday its members had not been paid on time at the Optimum coal mine, owned by the Gupta family, and would not return to work at the operation which has started business rescue proceedings.

Separately, the union said more than 500 workers will strike on Monday at Koornfontein Mine, which is also owned by the Guptas, over concerns of nonpayment of salaries.

India’s Bank of Baroda, which counts the Gupta family’s operations as clients, has pulled the plug on its South African business. South Africa’s main commercial banks have cut all ties with the Guptas, citing reputational risk.

NUM spokesman Livhuwani Mammburu said the union’s members were concerned the nonpayment of salaries was linked to the Baroda pullout as it was the last bank to service Gupta companies.

“The guys were not paid and they want a meeting with the CEO because they are concerned about the business rescue proceedings which they were not informed about,” he said, referring to workers at Optimum Coal.

He added that the workers would remain on strike until they are paid and they get clarity on the mine’s future.

Sbusiso Mahlangu, NUM Branch Secretary at Koornfontein, said: “We will down tools this coming Monday and we will not go back to work until our salaries are paid.”

The Guptas, who are Zuma’s business associates, have been accused of using their political connections to win state contracts and influence cabinet appointments. Zuma and the Gupta brothers deny wrongdoing.

The Optimum Coal mine east of Johannesburg supplies the fossil fuel to the Hendrina power station, part of the network of state-run utility Eskom which provides virtually all of the electricity for Africa’s most industrialized economy.

Eskom said on Thursday that coal had been diverted from other mines to supply the power station.

Koornfontein is an underground mine located south east of Johannesburg in the Mpumalanga province, which also provides coal to Eskom’s Komati power station.