(Screenshot taken from a video of the incident)

Excessive levels of carbon monoxide in a cinema in East China leading to 63 moviegoers being poisoned was caused by a fresh air system in a certain projection hall, the police investigation showed on Saturday.

A total of 63 moviegoers in a cinema in Dongyang city in East China's Zhejiang Province were poisoned after being exposed to excessive levels of carbon monoxide while watching a movie on Wednesday evening.

The investigation revealed that a fresh air system in No.3 projection hall inhaled the exhaust gas from the boiler, leading to the concentration of carbon monoxide levels in the hall, cctv.com reported Saturday.

“The inhale port of the fresh air system located on the fifth floor is only 0.5 meters away from an exhaust port of a pipe connected with a gas fired boiler on the first floor below ground (basement). This exhaust pipe emits carbon monoxide when the boiler is turned on,” Ma Jixiong, a police officer with the Zhejiang Provincial Public Security Bureau said.

After the incident, all 63 people in the movie hall were immediately rushed to hospital after suffering from symptoms such as fainting, vomiting and other physical discomfort for examination and treatment.

Five were identified with mild carbon monoxide poisoning and five others remained in the hospital for observation as of Friday evening.

At present, Dongyang city has instructed comprehensive safety inspection and special rectification for public and entertainment areas in the city.

The movie theater has since suspended its operations.

The incident quickly became a trending topic on China's Twitter-like Sina Weibo, with many Chinese netizens concerned about the safety of the people and the cinema.

One netizen pointed out that the cinema should be held responsible as an enclosed venue with poor ventilation during the pandemic.