BEIJING - A signal system design company apologized on Thursday for a design flaw in one of its products that allegedly caused Saturday's deadly high-speed train collision.

The Beijing National Railway Research and Design Institute of Signals and Communication posted an apology letter on its website on Thursday, expressing its condolences and regret to the victims of the accident and their families.

"We feel very sorry" for the deadly train accident that caused so much loss of life, the letter said.

The company promised to cooperate in investigations, take responsibility and shoulder any due punishments that may result from the investigations, the letter said.

Design flaws in railway signal equipment led to Saturday's fatal train collision near the city of Wenzhou in East China's Zhejiang province, the Shanghai Railway Bureau said earlier on Thursday.

After being struck by lightning, the signal system at the Wenzhou South Railway Station failed to turn one of its green lights to red, which caused the rear-end collision, said An Lusheng, head of the Shanghai Railway Bureau, at an investigatory meeting held by the State Council, or China's cabinet, in Wenzhou.

The signal equipment was designed by a Beijing-based research and design institute and was put into use on Sept 28, 2009, An said.

The accident has revealed the railway sector's vulnerabilities in safety infrastructure and management, An said.

The accident has left at least 39 people dead and 192 others injured so far.

The State Council has set up an investigatory panel to work at the site of the crash, the Ministry of Railways (MOR) said in a statement on Tuesday.