Johannesburg — Three prisoners were killed and 14 injured when the truck they were being transported in exploded, Gauteng police said on Monday.
Brigadier Neville Malila said one of the injured died later, taking the death toll to three.
The prison truck was transporting 36 awaiting trial prisoners from the Randburg Magistrate's Court to Johannesburg Central Prison.
"When they arrived at the corner of Naturena and the Old Soweto Highway, the driver heard a big bang. He noted there was a whole in the door and saw two prisoners escape."
The driver jumped out and arrested the two. On inspection at the prison it was discovered the vehicle had been blown open.
The remaining 19 prisoners were unhurt.
"Our forensic experts are currently combing the scene to determine the type of device used in the explosion."
Cases of murder, possession of explosives, and escape from lawful custody were being investigated.