Thirty-nine people died when a train ran into the back of another that had stalled on a viaduct near Wenzhou, after lightning cut off power supply.

The system "does not turn on the light green to red," said Director of Shanghai Railway Bureau Lusheng.

Chinese Premier Wen Jiabao, who visited the crash site, has promised to "severely punish" those responsible.

"The development of people, so the emphasis is on people's lives," said Wen at the site.

"No matter if it was a mechanical defect, a management problem or a manufacturing issue, we have to get to the bottom of this.

"If corruption is behind this, we have treated in accordance with the law and will not be smooth."

Wen previously promised to take steps to improve security for high-speed rail network - one of the government for these projects we hope will highlight the development of China.

Six cars derailed and four fell between 20m and 30m (65ft is 100 feet) away from the viaduct, after the incident Saturday night that injured 200 people.

The accident came just four years after the country's first high speed train began operating.

Rail experts warned against the rush to build faster and the world's longest high-speed rail network in the concerns of registration of the security center.

There are allegations that corners were cut during construction due to corruption, which raises the question of infrastructure throughout the country.

Martin Patience BBC in Wenzhou said it is difficult to get the truth because of the lack of transparency and accountability.

There is a real sense that perhaps things are being built too quickly and that security is compromised in the process, our correspondent.

"Public relations disaster"

Wen visited the scene of the accident comes the tightening of public shocked by the disaster.

Internet users and relatives of the victims were angered by the apparent reluctance of the government to answer questions about the accident.

This led the government to accusations of "arrogance", amid suspicions of a cover-up.

The authorities have moved quickly to stop the media, inviting reporters to focus on "very moving" stories, said the overall theme is "a great love in front of a big disaster."

Chinese media were ordered not to question the official line on the crash, but several newspapers published editorials critical of the Ministry of Railways.

Unusually high in an editorial published in both English and Chinese, told the state-run Times Wednesday overall government management of the post accident was "a public relations disaster."

"The relationship between the government and the public is like a ship and water. The water can keep the ship floating or sinking," he said.

Some relatives of victims, including two Americans and one Italian compensation, would have refused and instead demanded to give answers.

The incident is seen as the hopes of China's foreign sales shock trains in its efforts to become exporter of high technology.

Shares of the railroad and train builders in China have fallen sharply since the crash.