"It appears as if the brakes failed and the driver lost control," said Kenny Africa, the police traffic spokesman for the Western Cape Province. Two children were among the dead and 44 passengers were injured.
"We are recovering more bodies and the death toll may rise," Mr Africa told sources from the accident scene, adding it was unclear how many people were on board the bus.
The pass, situated in the picturesque Hex River Valley, is notorious for accidents because its straight and long descent allows vehicles to gather momentum before it leads suddenly into a dangerously sharp left turn.
Get Breaking news, live coverage, and Latest News from India and around the world on NDTV.com. Catch all the Live TV action on NDTV 24x7 and NDTV India. Like us on Facebook or follow us on Twitter and Instagram for latest news and live news updates.