Medupi is pictured in this file photo by Reuters.

Johannesburg - South African police said on Friday that 46 protesting workers had been arrested for public violence at the Medupi power plant site, the latest flare-up to hit the project after construction was suspended about a month ago.

State-run power utility Eskom has said the delays pose a “material threat” to the project, which is supposed to start generating power before the end of this year to ease a power crunch in Africa's largest economy.

“They were involved in public violence, closing the roads and setting cars alight. There was 46 arrested last night,” Simon Mpembe, the police commissioner in northern Limpopo province, told Reuters.

A spokeswoman for Eskom said construction “remained suspended.”

Labour unrest is a major concern for investors in South Africa. Wildcat strikes last year rocked the mining sector, triggering violence that killed over 50 people and hit output in the world's largest platinum producer. - Reuters