Four suspects have been put under criminal detention in connection to a gas explosion at a barbecue restaurant in Yinchuan, Northwest China’s Ningxia Hui Autonomous Region, which killed 31 people and injured seven. 

The four detained, including the legal representative of the restaurant surnamed Ma, a store manager surnamed Suo, and two shareholders surnamed Zhang and Liu, are under suspicion of crime of major accident liability, according to a statement from the Xingqing district branch of Yinchuan City Public Security Bureau released on Saturday. 

After investigation, the head manager of the barbecue restaurant surnamed Hai and a staffer surnamed Li, both who are dead, violated the relevant safety management regulations and replaced the pressure reducing valve connected with the liquefied gas tank without approval, resulting in the rapid leakage of liquefied gas from the tank and causing the explosion, according to the police statement. 

The public security organ will work with relevant departments for further investigation and crack down on illegal conducts according to the laws.

On Friday night, all 38 victims in the explosion were identified, said Xinhua. The seven injured currently show stable vital signs, with one already released from hospital.

The first batch of accident payouts have been made, according to China’s national financial regulatory administration on Friday night. 

Earlier, public security authorities have taken controlled of nine people including the manager, shareholders and working staff of the barbecue shop involved in the accident and have frozen their assets.

The other personnel remain is under investigation. 

The accident took place on Wednesday night in the city center of Yinchuan. According to public security and fire department records, the employee from the restaurant who called 119 said that they smelled a gas leak about an hour before the explosion and found that the liquefied gas tank valve was broken, so the manager of the shop went out to buy a new valve. The explosion occurred in the process of replacing the valve after the manager returned, media reported, citing local government.

China's State Council Security Committee held emergency video conferences and issued warnings about fire hazards and safety on Thursday. 

Yinchuan has started city-wide one-month safety overhaul after the accident. Many other municipal and provincial governments have also stressed safety production through emergency meetings.