A co-owner of Shanghai club Celia has confirmed that police raided the venue early Sunday morning, September 24 and conducted ID checks on patrons, subsequently detaining those who could not identify themselves.

In a WeChat message to Shanghaiist, Oytun Ergun said the police “were concerned with those who couldn’t provide a passport or a copy.” They prevented people from leaving the club as they conducted checks, and 20 people could not produce any identification. Those people were then taken to the police station and made to take a urine drug test. The police later told Ergun that 10 people tested positive for cannabis and other substances.

According to Ergun, this is the first time that police had raided Celia, and he insinuated that competitors and clubbers who were refused entry might have been behind the raids. The club also actively discourages drug use, Ergun said. We put “warning [signs] everywhere and I’ll check the toilets.”

According to Chinese law, all foreigners are supposed to carry their passports with them. Celia is currently closed but will reopen again on October 11.