A boilermaker died in an explosion near a production shaft of Sasol's Middelbult Colliery in Secunda on Thursday morning, the petroleum giant said.

Spokesperson Johann van Rheede said Ryno Olivier, 20, who was employed by Ukhozi Mining (Pty) Ltd, died on the scene of the accident when a container used for storage of oxygen and acetylene bottles exploded on surface.

Two other contractors and four Sasol mining employees also sustained slight injuries.

The exact cause of the explosion is still unknown, van Rheede said.

The outcome of the official investigation was still sub judice.

He said coal production was unaffected by the explosion.

Last Monday, a Sasol employee was killed in an explosion at a gas liquor storage tank at the mine's Secunda plant.

Dylan Ward, 21, apparently died when a fire broke out in the tank at the Phenosolvan West section.

Ward was one of eight employees doing maintenance work in area when the incident occurred. The seven other employees sustained minor injuries. - Sapa