An explosion at a small biotech company in northern China early Saturday killed eight people, China’s state media reported on Sunday.

The explosion occurred in Shuoyang in the Shanxi province in the early morning of Saturday, state media reported.

The legal representative of Jiapeng Biotechnology has been detained and the city has set up an accident investigation team, Xinhua News Agency reported.

The firm is located in a mountain hollow and dark yellow smoke was seen billowing from the accident site, Xinhua said.

Read More: China condemns Islamabad imambargah attack, pledges support

Reuters was not able to contact the company, which does not maintain a website.

The cause of the reported explosion was not immediately clear.

According to South China Morning Post, The workshop was located in a mountainous area over 40km from the Shanyin town centre.

 According to public records, Jiapeng Biotechnology was established on June 26 and its registered address is near a village in an area that was originally a mining site.

It was not licensed to handle dangerous chemicals.