Police say a "controlled explosion" at an explosives factory was the source of a blast heard by journalists on Sunday at the World Cup's main media center.
Col Eugene Opperman said the explosion was routine, and caused no injuries or damage. The noise could be heard in the media center at Soccer City, the main World Cup stadium in a gold-mining district on the outskirts of Johannesburg.
Brazil was set to play Ivory Coast at Soccer City later Sunday.
The South African Press Association said the factory was operated by Maxam Dantex in Roodeport and manufactures explosives for use in blasting at mines and quarries.