Three schoolchildren and their teacher were killed when a train collided with their bus at Mhala, near Bushbuckridge in Mpumalanga, police said on Monday.
"They were on a school trip when it happened. The bus was crossing the railway line. I am still waiting on the full report," Sergeant Gerald Sedibe said.
About 50 people were injured as they were heading home after a school trip to Pretoria between 3am and 4am.
The injured were taken to the nearby hospitals, where some were discharged the same day.
No further information was immediately available. - Sapa