The Ministry of Emergency Management will launch a thorough examination of all chemical factories to root out safety hazards in the wake of an explosion in Zhangjiakou, Hebei province, on Wednesday that killed 23 people.

The ministry's work safety bureau will set up 10 teams, comprising members of industry associations and experts, that will provide safety guidance and help it conduct in-depth investigations of 50 key counties with plants producing hazardous chemicals, Huang Ming, the ministry's Party secretary, said on Sunday.

It will also strengthen safety control and management with regard to the planning of plant sites and examine storage facilities for chloroethylene gas－an industrial chemical－at 75 enterprises across the country, he said.

The blast happened at 12:41 am on Wednesday at a chemical plant in Zhangjiakou's Qiaodong district. It triggered a chain of explosions, with flames engulfing 38 trucks and 12 other vehicles. The local authorities said in a micro blog post that 23 people were killed and 22 injured.

A preliminary investigation found that the accident was caused by a leak of chloroethylene gas from a storage facility at the Hebei Shenghua Chemical Industry Plant that burned fiercely when it encountered flames, resulting in a large number of casualties, the ministry said in an online statement on Friday.

The accident is still being investigated.

Huang said some local departments and enterprises failed to realize the seriousness of chemical safety control and did not assume sufficient supervision and management responsibilities.

He urged all local departments, factories and government bodies to clarify their responsibilities to form a strong supervision mechanism that can cover hazardous chemical industries.

It is also necessary to interview the people in charge of enterprises that have a high frequency of accidents and acute safety risks, Huang said.

To improve safety, the ministry will continue relocating chemical factories from populated urban areas and help update technologies and equipment.

Law enforcement will also be reinforced to act as a deterrent, he said.

"We should always remain alert in chemical safety matters," Huang said. "We should take up practical and hard work to continue to improve the safe production of hazardous chemicals."

Four of the 22 injured had left hospital by Friday, with 10 still hospitalized in Zhangjiakou and eight in Beijing. They are all in stable condition, the local authorities said.

Fifteen people at the factory have been detained by police.

"We will continue the investigation and severely punish those accountable according to law, and do our best to treat the wounded and carry out post-accident work," the local authorities said.