An employee at the Lethabo Power Station in the Free State died and another was seriously injured in a "major incident" on Wednesday afternoon, Eskom said.
The power utility said in a statement that police officials were on the scene at Unit 5 and emergency response teams had been activated.
"The Department of Labour has been notified and Eskom executives are travelling to the site... As a result of the rupture of a mainsteam pipe, the unit is not operational. Operations continue on the other units."
The employee's next of kin were being informed.
"Our condolences go out to the family and friends and we pray for the recovery of our injured colleague."
Energy expert Chris Yelland tweeted that there had been a boiler explosion.
Eskom confirms only Unit 5 at Lethabo is down after a generator trip followed by a loud boiler explosion. The other 5 units at @Eskom_SA's Lethabo PS are still operating, but staff have been evacuated as much as possible as a precautionary measure. Situation "calm" at the moment.— Chris Yelland (@chrisyelland) October 10, 2018
What's going on at #eskom? Fire again. It was very easy for #ThumaMina to destroy the technical excellence we put together over many years. It's becoming a mission impossible to rebuild. Indeed Eskom can't save itself pic.twitter.com/yOhYgzpbb1— Matshela Koko (@koko_matshela) October 10, 2018