Thursday's bus accident, in which it is feared that about 80 people have lost their lives, was the third major bus accident in which a bus plunged into a dam in the last 18 years.
Sixty-three people were confirmed dead after the bus in which they were travelling to a May Day rally in the eastern Free State plunged into the Saulspoort Dam, the African National Congress said on Thursday.
In March 1985, 42 high school pupils died in a similar accident when a Johannesburg municipal double-decker bus carrying the children home jumped the sidewalk and sank in the Westdene Dam in Johannesburg.
And in the mid-1990s, a bus carrying about 90 forestry workers to work plunged into a dam at Lothair, near the Swaziland border in southeastern Mpumalanga, claiming 38 lives.
The Westdene accident happened shortly after 1pm and it took police divers several hours to recover the bodies of the school pupils.
The bus itself, with its reverse lights burning and a reversing buzzer bleeping, was hauled out of the water six hours after the accident.
The bus driver and a number of children survived the accident.
Despite intensive investigations and a thorough inquest the real cause of the accident was never established.
Speaking from the Lothair police station inspector David Mlaza, who was at the scene of the Lothair disaster at the time it happened, said on Thursday it was disturbing that such tragedies continued to occur.
"I think the road safety authorities need to take another look at the roadworthiness of buses, the qualifications of drivers and the condition of roads." - Sapa