NINE people have been detained after Wednesday night’s deadly explosion at a Chinese barbecue restaurant, authorities said today.

The blast killed 31 people and injured seven at Fuyang Barbecue, a popular chain restaurant in Yinchuan, the capital of the Ningxia Hui autonomous region.

Those arrested, whose names have not been released, have also had their assets frozen, the official Xinhua News Agency reported.

The explosion in Yinchuan was followed on Thursday by an blast at a steel mill in China’s north-east that killed four people. 

An hour before the restaurant disaster, 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.

At a news conference on Thursday, the deputy head of the Communist Party in Yinchuan apologised to all people in the city, according to news site Huanqiu.com. Before the event opened, participants bowed their heads in silence.

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

He added that anyone responsible for the incident should be accountable under the law.

Mr Xi also ordered the launch of a national safety drive, telling all regions and related departments to address “all types of risks and hidden dangers” and initiate campaigns to promote workplace safety.

The president’s safety campaign is also likely to seek lessons from the explosion of a blast furnace at the Yingkou Iron and Steel Company on Thursday, which left four people dead and five others injured.

The cause of the explosion at Yingkou, in the province of Liaoning east of Beijing, is under investigation, the city’s Emergency Management Bureau said in a statement, while adding that experts believe that an equipment malfunction was to blame.