BEIJING, Jan 7 (AFP) — At least 20 people were trapped after an explosion on Friday caused a building housing a government canteen to collapse in the Chinese city of Chongqing, according to state media.

The blast at 12:10 pm (0410 GMT) was caused by a “suspected gas leak” in a canteen and caused a neighborhood committee building to collapse, trapping people inside, the state-run People’s Daily reported.

Authorities have sent around 260 rescue workers and 50 vehicles to the site, state broadcaster CCTV reported, adding that the cause of the blast was under investigation.

A video posted on the official Weibo page of China’s fire department showed orange-clad workers in hard hats climbing through large chunks of rubble.

Nine people have been rescued from the site, the department said.

Official news agency Xinhua said some injured people had been taken to hospital, without giving further details.

Footage posted on social media by CCTV showed smoke and dust billowing from the collapsed building in Wulong district on the outskirts of the southwestern megacity.

An eyewitness told state-run Phoenix TV that the blast was “very scary… our windows have all been blown to pieces”.

Local government officials have set up an “on-site emergency response headquarters” to direct the rescue work and provide medical treatment, People’s Daily reported.

Gas leaks and explosions are not uncommon in China, due to weak safety standards and corruption among officials tasked with enforcing them.

In June, 25 people were killed in a gas blast that ripped through a residential compound and struck a busy two-storey building packed with shoppers.

Eight suspects, including the general manager of the company that owned the gas pipe, were detained after the government said “the company’s safety management system was unsound”.

The same month, 18 people were killed and more injured when a fire broke out at a martial arts school, with state media reporting that all the victims were boarding school pupils.