A fire tore through a martial arts training centre in China’s Henan province on Friday killing at least 18 people, local authorities said.

The blaze broke out at 3 a.m. (1900 GMT Thursday) and has since been extinguished, the Zhecheng county government said in a statement on its website.

It was unclear what had caused the fire, which injured 16, four of whom were in a serious condition, the county government said.

The person in charge of the centre has been detained by the police, according to the statement.

The name of the martial arts centre was not disclosed.

Outbreaks of fire in China are not uncommon, with patchy safety protocols and sub-standard construction a frequent concern.

In one of the province’s most horrific fires, 309 people died in the city of Luoyang on Christmas Day in 2000 at a night club. Most of the victims suffocated by smoke in the dance hall, which had only two emergency exits, and no sprinklers or smoke alarms.