Eskom said on Wednesday that it is operating normally despite protests by workers outside four of its power plants following a breakdown in wage negotiations.

Police surrounded five of the stations earlier when protesters tried to block other employees from arriving for night shifts. Eskom has put in contingency measures to ensure supply.

“We are hopeful our ability to continually generate electricity will remain sustainable, but the situation is not ideal,” spokesman Khulu Phasiwe said by phone. Eskom’s power stations and other facilities “continue to operate optimally”, he said.

Wage talks between Eskom and unions broke down last week, with labour organisations saying they’re planning a protest march on Thursday after the cash-strapped utility insisted it can’t offer any pay increases. Because the power producer is considered to provide an essential service, legally workers are not permitted to strike.

The utility is taking measures to improve its finances as demand has lagged since rolling blackouts in 2015 curbed the country’s economic growth. In addition to scrutinizing its business model, it’s reining in costs.

The National Union of Mineworkers and National Union of Metalworkers of South Africa said at a joint press conference on Tuesday that they would exhaust all legal measures following the breakdown in wage negotiations last week. A NUM spokesman couldn’t immediately comment on Wednesday.

“We are waiting for information from our regions regarding events as they unfold in Mpumalanga,” Numsa spokeswoman Phakamile Hlubi said in a text message response. “The official day of action is the march which happening at Megawatt Park tomorrow,” she said, referring to Eskom’s head office.

Phasiwe said the action has been largely peaceful, with some burning of tyres.

“In the morning today around 3am, that’s when some of the protesters were trying to go into our power stations to blockade the road,” he said. However police on the site were “quick off the mark”. — Reported by Amogelang Mbatha, Paul Burkhardt and Odwa Mjo, (c) 2018 Bloomberg LP