“The management got a call around 7AM or 7.30AM from an unknown man who said there is a bomb at the site,” Brigadier Hangwani Mulaudzi said on Saturday.
“We got there and evacuated at least 6000 workers. Our bomb unit and dogs are combing the site,” he said.
The power plant would be closed for the day and pedestrians were being redirected around the area.
Mulaudzi said the threat had nothing to do with a strike by workers.
On May 10, a protest by about 500 workers led to the closure of the site after vehicles were damaged.
Medupi is a new dry-cooled coal-fired power station being built by Eskom, scheduled to be fully operational by 2015.