Created on Thursday, 28 July 2011 15:30
Serious flaws in the signalling system caused a fatal collision on China's high-speed rail network, officials say.
Thirty-nine people died when one train ran into the back of another, which had stalled on a viaduct near Wenzhou after lightning cut its power supply.
The system "failed to turn the green light into red", said An Lusheng, head of the Shanghai Railway Bureau.
Chinese Premier Wen Jiabao, who has been visiting the crash site, vowed to "severely punish" those responsible.
"The country's development is for the people, so the most important thing is people's lives," Mr Wen told reporters at the scene.
Mr Wen earlier promised to take steps to improve safety on the high-speed rail network - one of the government's flagship projects which it hopes highlights China's development.
Six carriages derailed and four fell between 20m to 30m (65ft to 100ft) from the viaduct after Saturday night's crash, injuring nearly 200 people.
The accident came just four years after the country's first high-speed trains began operating.
Rail experts had warned against the rush to build the world's longest and fastest high speed rail network in record time amid safety concerns.
Comparisons have been drawn with Japan's bullet train system, which has had no major accidents since it started running in 1964.
Mr Wen's visit to the crash scene comes amid growing public outrage at the accident.
Internet users and relatives of the victims have been angered by the government's apparent unwillingness to answer questions about the crash.
This has led to accusations of government "arrogance", amid suspicions of a cover-up.
The authorities have moved quickly to stem media coverage, urging reporters to focus on "extremely moving" stories, saying the overall theme should be "great love in the face of great disaster".
Chinese media have been ordered not to question the official line on the accident, but several newspapers have published editorials criticising the railway ministry.
In an unusually scathing editorial published in both its English and Chinese versions, the state-run Global Times on Wednesday called the government's handling of the accident aftermath a "public relations disaster".
"The relationship between the government and the public is like that of a ship and water. Water can keep the ship afloat or sink it," it said.
Some relatives of victims, who include two Americans and an Italian, have reportedly refused compensation and demanded instead to be given answers.
The accident is also a huge blow to China's ambitions to sell its high-speed rail technology overseas.