TOKYO, March 8: A Tokyo commuter train carriage jumped off the rails Wednesday and skidded into an on-coming train, killing three passengers and hospitalising 31, officials said."The back part of the train derailed but we don't know the cause," said a Tokyo metropolitan police spokesman. The derailed carriage, still attached to the train, then "skidded for 100 meters (yards)," a transport ministry official who inspected the site told reporters there. It collided with an oncoming train on the neighbouring track of the city's busy Hibiya Line. The crash at 9.10 am at Nakameguro station, central Tokyo, killed three passengers and hospitalised 31, including two critically injured, according to latest figures from the Tokyo fire department. One woman had been listed as unconscious after the crash but she died later in hospital, said a police official. Another man suffered heart and lung failure but doctors were fighting to save him, said fire department spokesman Yoshio Ogawa. "Doctors put him on a breathing machine and are massaging his heart. He is trying to survive," he said. "I heard a loud metallic sound like a big crash. I felt the shock," said 56-year-old businessman Toshio Murata, who was travelling on the train just behind the wrecked section. "I saw some rescue workers taking away the train's side and carrying out injured passengers," he told AFP. "One woman was carried out on a stretcher with her clothes ripped apart and stained in blood." National television showed pictures of a man being wheeled into nearby Hiroo Hospital, central Tokyo, with a bandage around his head. Rescue crews wheeled in another victim on a stretcher. The entire side of the last carriage on the doomed eight-carriage train, carrying an estimated 240 people, was ripped away, but it remained standing just a few meters off the track. Tangled metal lay across the carriage and seats had been torn from their moorings in the floor. "I apologise to the victims from the bottom of my heart," said Kiyoshi Terashima, President of Teito Rapid Transit Authority which operates the main Tokyo subway system. "Our company and the transport ministry are doing their best to clarify the cause of the accident as quickly as possible. We are ready to take sincere measures to the victims," he told a news conference. Transport Minister Toshihiro Nikai told parliament the cause was unknown. "I extend my deepest condolences to the families of the dead." About 350 firefighters with 20 engines, dozens of police cars and several ambulances had crowded into a nearby road below the raised railway tracks to take away the dead and injured.Earlier reports that the train had been wrecked by an explosion proved wrong. "I am going to get a detailed report and we will handle this swiftly," promised Prime Minister Keizo Obuchi. "It was not an explosion, it was a derailment." Police were speaking to the driver of the wrecked train, said a spokeswoman for the Teito Rapid Train Authority. "We don't know how long the investigation will take. The driver is at the site to help police investigations of the accident," she said. The Hibiya Line runs above and below ground through central Tokyo carrying 1,155,000 passengers a day, with trains running every two minutes and 30 seconds during the morning rush hour. Services were being slowly restored and a railway official said the wrecked train would likely be removed later in the day.