More than 850 people have been injured in a train crash during Thursday's evening rush hour in the South African township of Soweto in Johannesburg, the train operator Metrorail has said. A commuter train hit a stationary one from behind, the force of which threw some passengers through windows. Three of the casualties were in a critical condition, officials said. Correspondents say most of the injured were treated at the scene, in one of the biggest rail incidents for years. According to the authorities, 25 of the injured are still in hospital. South Africa's Railway Safety Regulator (RSR) said it was investigating the cause of the crash, which occurred at 1750 local time (1550 GMT). 'Chaos' Local television news pictures showed casualties being treated at the scene by medics - some of them tended to by torchlight. Metrorail, which is responsible for running the trains and is heading the salvage operation, told the BBC that 857 people had been injured in the accident. Medical rescue official Jeff Wicks told the Sapa news agency there had been "chaos" at the scene. "We had people who were sprayed 200m around the trains... on arrival, paramedics found passengers from both trains lying on the track," he said. According to Pretoria News, people lay groaning in the dark, with some waiting more than an hour before being transported to hospital. Synock Matobako, a spokesman for the emergency services, said they had had to request more ambulances because of the number of casualties. "This is the biggest incident in recent years, even though no-one has died. People sustained serious multiple injuries." Fire rumour Evason Mogomotsi, who was on the train, told the BBC he was dozing on the train and woke up when it crashed. "After the crash, people started screaming and many were trying to get out of the train," he said. "There was also a rumour that the other train had caught on fire so people were trying to escape. "Some people were even trying to stand on the people who had fallen in order to get out of the train." Another passenger, Gladwell Ntusi, said some people jumped out of the windows. "It was horrible, I saw people with broken legs, others had cracked their temples. It was not a nice scene," he told reporters. The Metrorail train had been travelling between Mzimhlophe and Phomolong in Soweto. More than two million passengers travel daily on South Africa's commuter trains. Source: BBC