JOHANNESBURG (Bloomberg) - Petroliam Nasional Bhd.'s Engen oil refinery in Durban, South Africa's third-biggest, cut output 40 percent after a fire.

The blaze, which started in a vacuum unit used to make feedstock for asphalt and lubricants, will reduce production at the 125,000-barrel-a-day refinery for three weeks, Herb Payne, a plant spokesman, said today in an interview from Durban. The fire was caused by a leak and was put out within about 10 minutes of starting at 3.15 p.m. local time.

The fire is the second at the plant within a month. On November 19, lightning struck a fuel storage tank, causing a three-day fire that resulted in the loss fuel and equipment valued at as much as 120 million rand ($17.8 million).

The largest refinery in South Africa is Sapref, also in Durban and owned by BP plc. and Royal Dutch Shell plc., followed by Sasol Ltd.'s plant southeast of Johannesburg.

South Africa's crude oil refineries import most of their supplies from Saudi Arabia, Iran and Nigeria, according to the US Energy Department.

Petroliam Nasional, known as Petronas and Malaysia's state oil company, supplied 26.5 percent of the gasoline sold in South Africa last year.