By Rogan Ward and Wendell Roelf
DURBAN (Reuters) - An explosion rocked South Africa's second-largest crude oil refinery in Durban on Friday injuring seven people, local emergency services said.
Engen, which operates the plant and is majority owned by Malaysia's Petronas, said a fire broke out at around 0510 GMT and was extinguished by 0645 GMT.
"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.
The extent of damage or the impact on production at the 120,000 barrels per day (bpd) refinery was not clear.
Those injured are in a stable condition, KwaZulu-Natal emergency medical services spokesman Robert McKenzie said.
Engen said in a statement that the cause of the fire was under investigation. It made no mention of injuries or output and said it would provide another update later.
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 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, 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 and Alexander Smith)