The agitated son of a Hong Kong resident who went missing last Friday, after being intercepted and interrogated by mainland Chinese agents at a border checkpoint while en route to Macau, has finally learned the whereabouts of his father – and the reason for the detention.

The family of the Hong Kong man surnamed Chung, 53, was told by the city of Zhuhai’s public security bureau that he had been nabbed to assist in the investigation of a smuggling case that occurred seven years ago, on suspicion that he was a kingpin of a crime syndicate. Chung is believed to be in custody in the mainland city in Guangdong province bordering Macau, after he lost contact the moment he messaged his family about his arrest.

The man was reportedly whisked away as a “wanted fugitive” while passing through a temporary security check station set up on the eastern artificial island of the Hong Kong-Zhuhai-Macau Bridge. Since early December all cross-boundary passengers heading for Macau and Zhuhai via the mega bridge-tunnel structure across the Pearl River estuary have been subject to additional screening.

Normally, Hong Kong residents, including foreigners holding the city’s ID cards and passports, only need to go through immigration checks from Macau authorities – not mainland officials – when they use the mega bridge to go to the gambling hub.

Chung is the latest addition to a growing number of residents, journalists and expats from Hong Kong who have been either detained or turned away by mainland or Macanese officers since October, as the former Portuguese colony counts down to its celebrations marking 20 years under Chinese rule since 1999. Xi Jinping and his wife Peng Liyuan are expected to fly in this Wednesday to preside over a flurry of events.

Earlier this month, Tara Joseph, President of the American Chamber of Commerce in Hong Kong, and the influential business group’s chairman, Robert Grieves, were both kept in an immigration facility for questioning for two hours by Macau’s immigration authority and subsequently were refused entry. The pair had intended to visit the city to attend a business banquet co-organized by the chamber.

“Both Robert and Tara were given no reason for why they were delayed,” read a statement from the chamber. “After several hours, and after having to sign a statement that they voluntarily agreed not to pursue entry into Macau, they both returned to Hong Kong without any difficulty.”

The statement added: “We are puzzled as to why this happened, given this was simply a social occasion to celebrate AmCham Macau’s annual gathering…. We hope that this is just an overreaction to current events and that international business can constructively forge ahead” in Macau.

There also were reports on Tuesday that two journalists from Hong Kong’s Now TV, ultimately owned by tycoon Li Ka-shing’s business empire, have been sent back by Zhuhai officers deployed on the bridge’s eastern artificial island after they were searched and questioned.

Macau authority had similarly denied entry to Hong Kong pro-democracy lawmakers, activists and academics. It is rumored that the city has been given a blacklist of unwelcome persons, a list that is updated by the mainland from time to time.

The Hong Kong government insists that interfering in the law enforcement activities of other jurisdictions would be improper even when its residents are arrested or turned away. Hong Kong authorities stress that Macau has its own autonomy in granting or refusing entry to anyone and that the new security check posts on the sea-crossing bridge are located outside Hong Kong waters.

The tiny gaming enclave of about 33 square kilometers is in a security lockdown this week. Given Macau’s small size and its police’s manpower constraints, it is said that municipal and provincial cadres in Zhuhai and Guangdong have already taken over the territory’s policing arrangements and emergency response, to ensure absolute security for Xi and his entourage.

Zhuhai just wrapped up a massive antiterrorist drill a few weeks ago inside the mainland control area of the sea-crossing bridge.