By Rogan Ward and Wendell Roelf

DURBAN (Reuters) – South Africa’s second-largest crude oil refinery, the Engen plant in Durban, has been shut down to allow investigators a chance to find out the cause of a “fire incident” earlier on Friday, Engen said.

Engen, which operates the 120,000 barrel per day plant and is majority owned by Malaysia’s Petronas, said a fire broke out at around 0510 GMT and was extinguished by 0645 GMT.

“Engen is currently assessing its overall bulk fuels supply and demand position and implementing immediate mitigations to manage inventory and product supply requirements,” Engen said in an update.

Local emergency services said seven people were injured, although Engen said no injuries were recorded and all refinery personnel were accounted for.

“I saw a massive fireball at the center of the refinery with thick black smoke billowing from it,” Durban resident Shane Lloyd Pretorius told Reuters.

Engen said in a statement that the cause of the fire was under investigation.

A Reuters witness at the scene saw several fire engines spraying foam onto the affected part of the refinery, as well as ambulances, metropolitan police and national police standing by.

Africa’s most industrialized 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, also suffered an explosion earlier this year.

Top refinery SAPREF, which is also located in Durban and is a joint venture between BP and Shell, said the incident at Engen’s facility had no impact on its operations.

The Engen Refinery and SAPREF form part of a major petrochemical hub on the east coast close to Durban’s port.

(Additional reporting by Alexander Winning in Johannesburg and Ng Yi Shu in Singapore; Writing by Alexander Winning; Editing by Himani Sarkar, David Evans, Alexander Smith, Kirsten Donovan)