Thirty people, most of them British tourists, were killed yesterday and seven others badly injured when their bus went off the road in South Africa's Mpumalanga province, police said.
The accident happened when the coach with 37 people on board overturned on a mountain pass, four km outside the town of Lydenburg, around 250 km northeast of the capital, Pretoria.
In London, a spokesman for British tour company Thomas Cook said the tour involved 34 British holidaymakers and three tour personnel, one of whom was British.
Thirty passengers were travelling with Thomas Cook, four with South African Airways. All 34 had been due to fly back to Britain on Friday, the spokesman added.
Fourteen survivors, including the South African bus driver, were rushed to nearby Lydenburg hospital, but seven died as doctors fought to save their lives, a police spokesman, Mr Mandla Mahlangu, said.
The Lydenburg hospital manager, Ms Cathy Olivier, described the condition of the survivors as "severely injured".
Three were yesterday evening being transferred to a regional
hospital in the town of Witbank, 150 km east of Pretoria. A hospital spokeswoman said that one was in a "very critical" condition, while the other two had head injuries.
Police began an immediate inquiry into the cause of the accident. They had been able to question the driver. Brake failure was being investigated as a possible cause of the crash.
Police said 23 people died at the scene of the crash, which happened shortly after noon. The roof of the bus had been ripped off.
Mr Mahlangu said a passenger manifest found at the scene of the crash listed the passengers as British nationals.
He was expecting a British consular official at the scene in the evening and London confirmed that two were being sent from Pretoria. Mr Simon Laxton, general manager of Thomas Cook Holidays, said: "This is a tragic and devastating accident and we're doing everything humanly possible to confirm details of fatalities and injuries."
The Thomas Cook spokesman said the company had already mobilised a five-strong team to travel out to South Africa. This included engineers, legal advisers and customer service representatives.
The foreign ministry in Pretoria said the government was "deeply shocked and saddened by the news" of the accident.
"The South African government expresses its condolences to the government of Great Britain as well as to the families and friends of those who died," a statement issued by the ministry said. Police said it appeared the driver of the bus, operated by South African firm Springbok Atlas tours, lost control of the vehicle as it negotiated Long Tom pass, a scenic mountain pass between Lydenburg and Sabie, popular with tour groups.
The area is close to several Anglo-Boer war battle sites and game reserves.
Police said the wrecked bus had come to rest on its side some 10 metres off the roadside, which at that point is steep and narrow. Marks on the roadside showed it had left the road some 150 metres away.
Bodies and the occupants' personal luggage and personal affects were strewn over the nearby hillside. The accident is the fifth major bus crash in South Africa since last Wednesday, taking the total death toll to 62 with more than 160 injured.