Seven people have been injured after an explosion rocked South Africa’s second-largest crude oil refinery in Durban.

Engen, which operates the plant and is majority-owned by Malaysia’s Petronas, said a fire broke out about 7.10 am (05:10 GMT) on Friday and was extinguished by 8.45 am (06:45 GMT).

The extent of damage or the effects on production at the 120,000 barrels per day (bpd) refinery were not clear. Engen said in a statement that the cause of the fire was under investigation.

Those injured are in stable condition, KwaZulu-Natal emergency medical services spokesman Robert McKenzie said.

All seven injured were workers at the refinery, paramedic Garrith Jamieson was quoted as saying by The Associated Press.

He said six of the workers were being treated for smoke inhalation and the other injured their hip in a fall while trying to escape the fire.

Reuters news agency quoted a witness at the scene saying several fire engines sprayed foam onto the affected part of the refinery, and reported ambulances, metropolitan police, and national police standing by.

“I saw a massive fireball at the centre of the refinery with thick black smoke billowing from it. A few minutes later many vehicles passed by my home,” Durban resident Shane Lloyd Pretorius told Reuters.

Africa’s most industrialised economy has six refineries, four using crude oil and two synthetic fuel as feedstock. It is a net importer of petroleum products.

The country’s third-biggest crude oil refinery, a 100,000 bpd facility operated by Astron Energy in Cape Town, was the site of an explosion earlier this year.

Videos and pictures of a massive fire at the Engen refinery in Durban South coming through. This follows an explosion there. Emergency services personnel are at the scene. #eNCA pic.twitter.com/CMWVlNYKWt

— Dasen Thathiah (@DasenThathiah) December 4, 2020