Six mine workers died and 28 others were injured after the bus they were travelling in was set alight outside Driekop in Limpopo on Monday evening.
"Two people who pretended to be mine workers, got onto the bus and set it alight. They then got out and fled," Limpopo police spokesperson Brigadier Motlafela Mojapelo said on Tuesday.
He said six workers were burnt beyond recognition. The bus driver and the 28 other workers escaped through windows.
The injured workers were taken to hospital.
Mojapelo said the workers were from Modikwa Platinum Mine in Burgersfort, Limpopo.
Mojapelo added that a reward of R500 000 would be offered to anyone with information that could lead to the arrest and possible conviction of those responsible for the "horrific incident".
Mine representatives could not be reached for comment.
Provincial Commissioner Lieutenant General Nneke Ledwaba said the police would not rest until arrests have been made.
"We call on community members to assist the police in their quest to swiftly crack this case and any valuable information received will be treated with the strictest confidentiality," Ledwaba added.
Anyone with information can contact Captain Richard Boshomane on 079 894 5501 or Warrant Officer Bethuel Mahlatji on 079 657 6873. They can also call the toll-free Crime Stop number 08600 10111.