Beijing has a new imperative to stem the “infiltration” of information about the protests in Hong Kong which involves the city’s residents being stopped, detained and interrogated by Chinese security and immigration agents at major checkpoints when they cross the border to the mainland.

It was reported that some black-clad Hongkongers – the color of the city’s ongoing demonstrations against a China extradition bill – were intercepted by mainland officers while crossing the border to Shenzhen in mainland China.

They were made to open their bags and surrender and unlock their smartphones and other handsets for an “inspection,” and once any photos, video clips or texts in support of the rallies were found, they would face prolonged detention, in some cases hours.

They would be further questioned if they participated in the protests or if they opposed the Communist Party of China. Some also had their fingerprints and blood and DNA samples taken.

Hong Kong’s Apple Daily reported that such extra checks targeting Hongkongers wearing black T-shirts and blouses had been in place since June at major border checkpoints including Luohu and Futian. Both are served by metro lines with hundreds of thousands of passengers passing through there each day.

The broadsheet noted that, however, such checks were conducted randomly. Those chosen would be asked to go a small, cordoned-off area in a corner of an arrival hall for inspection of their luggage and phones.

But other newspapers warned that Beijing had already ramped up efforts to check more Hongkongers entering the mainland, regardless of the color of their clothes.

Chinese border security and immigration agents stand guard inside an arrival hall. Photo: Weibo
Shenzhen’s Luohu checkpoint. Hongkongers need to make sure their phones won’t contain ‘politically incorrect’ information before crossing the border. Photo: Asia Times

One Hongkonger, who was detained for five hours at the end of last month, told reporters that he was transferred to a police station in Shenzhen’s Luohu district after mainland agents found a dozen photos of the protests as well as his own selfies from the site.

He was then ordered to provide personal information about his home address in Hong Kong, address on the mainland, phone number, occupation, education background as well as names and contact details of family members.

He said the officers took mugshots of him, collected his fingerprints and DNA samples via a finger prick, which made him wonder if they thought they were dealing with a felon or terrorist. He was released five hours later after making a statement admitting he was arrested for spreading “malicious” information.

Some pro-democracy lawmakers say Hong Kong’s Security Bureau should contact mainland authorities and demand an explanation, and in the meantime, they reminded Hongkongers to back up the content of their phones and delete sensitive photos and videos before going across the border.

Beijing has also moved to segregate popular social networking platforms like WeChat and Weibo, as posts by Hong Kong and overseas users were deemed politically incorrect and were swiftly censored.

A file photo shows protesters gathering outside the headquarters of the Hong Kong police in June. Photos depicting large crowds like this will likely be censored by WeChat. Photo: AFP/Hector Retamal

Asia Times also discovered that WeChat has been deploying advanced machine learning and image recognition technology to delete or blot out photos of the protests in Hong Kong uploaded by users to their personal pages.

“Problematic” photos and posts circulating on the platform will be insulated and taken offline to make sure mainlanders will never be “instigated,” but overseas users will still be able to see them.

Read more: PLA video warning for Hong Kong