A COOKING gas leak is believed to be the cause of a massive explosion at a barbecue restaurant in north-west China that killed 31 people and injured seven.

Wednesday evening’s blast came during national celebrations on the eve of a long holiday weekend, authorities said today.

People were gathering at the restaurant on a busy street in Yinchuan, the capital of the traditionally Muslim Ningxia Hui autonomous region, ahead of the Dragon Boat Festival when the explosion occurred, the official Xinhua News Agency reported.

Many people were left unconscious and needed to be carried out of the building, according to news website The Paper, which quoted a member of the search and rescue team. 

Victims included elderly people and high school students, it added.

An hour before the explosion, employees noticed a smell of cooking gas and discovered that a gas tank valve was broken, according to Xinhua. 

The blast occurred while an employee was replacing the valve.

Chinese President Xi Jinping demanded urgent medical care for the injured and a safety overhaul after the explosion, Xinhua said. 

He urged efforts to quickly determine the cause of the accident and hold people accountable under the law.

Mr Xi also said that all regions and related departments should address “all types of risks and hidden dangers” and launch campaigns to promote workplace safety.

The incident happened at Fuyang Barbecue, a two-floor chain restaurant popular for its grilled skewers and stir-fried dishes, The Paper reported. 

The Ministry of Emergency Management posted on social media that search and rescue work at the restaurant had been completed by early today and investigators were now working to determine the cause of the blast.