At least seven people have been treated for smoke inhalation after an explosion rocked the Engen refinery in South Africa's Durban City on Friday morning, the local government confirmed.

"At this stage seven people have been treated for smoke inhalation. All are reported to be in a stable condition," the government of KwaZulu-Natal province, where the refinery locates, tweeted.

Disaster management and emergency response teas have been dispatched to the scene.

The fire has been extinguished, and the cause of the incident is under investigation. 

A media report said the blast happened at 7 a.m. (GMT 0500) and was heard about 25 kilometers away.

According to Engen's website, the Durban refinery has a crude refining capacity of 120,000 barrels per day. It is the second-largest crude refinery in South Africa.

(With input from agencies)

(Cover image via @kzngov)