A gas leak caused a restaurant in Yinchuan, northwest China, to explode and kill at least 31 people, state media reported today.

The explosion happened on the night before the Dragon Boat Festival holiday, when many people in China go out with friends.

State broadcaster CCTV showed footage of firefighters at the scene, with smoke coming out of a big hole in the restaurant’s front. Glass and other pieces were scattered on the street, where there are also other restaurants and entertainment places.

Police held nine people, including the restaurant’s “owner, shareholders and staff”, after the blast, CCTV said. It also said “their assets have been frozen”.

State news agency Xinhua said the regional Communist Party committee blamed a leak of liquefied petroleum gas for the explosion at a barbecue restaurant on Wednesday night.

Seven people were still in hospital, it said, with one in a “critical condition”.

Two had severe burns, two had minor injuries and two had scratches from flying glass, Xinhua said.

The Paper, a state-backed media outlet, said high school students and retirees were among the dead, who mostly suffocated from smoke inhalation. It quoted unnamed officials who helped with the rescue.

The blast happened at 8.40pm last night at the Fuyang Barbecue Restaurant in downtown Yinchuan, the capital of Ningxia autonomous region.

Xinhua said today that Chinese President Xi Jinping “ordered full efforts to treat the wounded and to strengthen safety supervision and management in key industries and fields to protect people’s lives and property”.

Xi also “called for efforts to find out the cause of the accident soon and to punish the relevant people according to the law”, it said.

”All regions and related departments should check and fix all kinds of risks and hidden dangers,” Xinhua said Xi said.

The Ministry of Emergency Management said more than 100 people and 20 vehicles from local fire and rescue services went to the site after the explosion.

Local authorities “quickly… asked for all-out search and rescue efforts, proper treatment for the wounded and less casualties as possible”, it said.

The rescue efforts ended by 4.00am today, it said.