President Cyril Ramaphosa has said that sabotage contributed to recent uninterrupted load shedding.
Ramaphosa is briefing the media on Eskom after cutting short an official visit to Egypt.
The president said that while a number of factors contributed to recent rotational power cuts, including heavy rains, unplanned outages and the age of power stations, about 2 000MW of power was also lost due to an act of sabotage.
"What has also come out as a great concern is that there has been a measure of sabotage, sabotage that has lead to the loss - during this period - of 2 000MW, where someone in the Eskom system disconnected one of the instruments that finally lead to one of the boilers tripping, and us losing as much as 2 000MW".
Ramaphosa said the act of sabotage must be investigated, and Eskom must work with the police and intelligence services to find out what happened.
He added that from December 17 to January 13 there would likely not be load shedding. "All leave is cancelled. No one goes on leave," he said.
The power utility called the briefing at its Megawatt Park headquarters in Johannesburg after days of rotational power cuts, including the unprecedented implementation of stage 6 load shedding on Monday evening, which forced mines countrywide to bring underground operations to a halt.
READ| Eskom's Oberholzer: 'Grid has been abused for far too long and we're now reaping the reward'
The briefing comes after the struggling power utility and government faced a flood of criticism over the rolling blackouts, including from the South African Chamber of Commerce and Industry, which said on Tuesday that the state should reevaluate whether it has the "necessary competencies, skills and experience" to manage the organisation.
Market research company Intellidex, meanwhile, said the effects of sustained load shedding may slash SA's 2019 GDP growth to just 0.3% from 0.4%.
Union representatives, meanwhile, say Eskom staff are overworked and battling low morale.
The briefing continues.