Chinese Premier Wen Jiabao has vowed to punish anyone involved if there was corruption that caused a high-speed train crash that killed at least 39 people, amid growing public resentment of the handling of the accident.
Mr Wen, speaking to reporters at the site of the crash between two bullet trains last weekend that also hurt 190 people near the eastern city of Wenzhou in Zhejiang Province, said that a "serious investigation" was under way and that results would be made public.
"No matter if it was a mechanical fault, a management problem, or a manufacturing problem, we must get to the bottom of this," Wen said. "If corruption was found behind this, we must handle it according to law and will not be soft. Only in this way can we be fair to those who have died."
Mr Wen's comments were made shortly after a railway official said design flaws in signal equipment and human error caused the crash.
Six train cars derailed and four fell about 65 to 100 feet from a viaduct on Saturday night after one train ploughed into the back of another train that had stalled after being hit by lightning.
An Lusheng, head of the Shanghai Railway Bureau, said there were design problems with the signal light equipment at the Wenzhou South station and dispatchers did not send any warnings after the lightning strike.
"After the lightning strike caused a failure, an interval signal machine that should have shown a red light mistakenly upgraded it to a green light instead," Mr An said in comments carried by state broadcaster CCTV.
The Beijing National Railway Research and Design Institute of Signal and Communication, which designed the signal equipment, on Thursday issued a letter of apology to the families of the victims and the injured passengers.
It said it would cooperate with the investigation and would "have the courage to assume responsibility and accept the punishment deserved".