A Hong Kong man working for the British consulate was recently detained in mainland China when he was returning to Hong Kong from Shenzhen.

The 28-year-old man named Simon Cheng is a trade and investment officer at the British Consulate General in Hong Kong.

A day after his family went public with his disappearance for more than 10 days, the Shenzhen police apparently confirmed his detention.

The reason? For soliciting prostitutes.

Detained for prostitution: Shenzhen police

Chinese state media Global Times reported on Thursday, Aug. 22, that the Shenzhen police had detained Cheng for violating the "66 article of China's law on administrative penalties for public security".

The article stipulates that those who "engage in prostitution or visiting prostitutes shall be detained for not less than 10 days but not more than 15 days".

In addition, they may be fined not more than 5,000 yuan (S$978).

The detention was confirmed by Geng Shuang, the spokesperson for China's Ministry of Foreign Affairs (MFA), at a regular press conference on Wednesday, Aug. 21, according to Global Times.

Cheng's family has also confirmed this, according to a second statement they put up on Aug. 22, saying they received news from the Chinese MFA that Cheng is currently under a 15-day administrative detention for violating the Public Security Administration Punishment Law.

An "administrative detention" allows an individual to be held without being charged.

Went missing after going to Shenzhen for 1-day business trip

Cheng had left Hong Kong in the morning of Aug. 8 to go to Shenzhen, China, for a business trip.

Before passing through immigration customs at about 10:45pm at night on the same day, he had sent a text message to his Taiwanese girlfriend, surnamed Li, on WeChat, saying, "Pray for me".

But Cheng never arrived in Hong Kong.

His family lawyer could not find his whereabouts in local detention centres and police stations, nor could they get information on why and how long he would be detained for.

More than 10 days later, they posted a statement on Aug. 21 detailing his disappearance, and the steps they took to track him down, but to no avail.

If the Shenzhen police's words are anything to go by, Cheng should be back home safely in a few days' time.

Detained at West Kowloon station

According to Financial Times, Li said Cheng was at the West Kowloon station, which allows travellers to go between Hong Kong and Shenzhen via high-speed rail.

The station’s immigration checkpoint area is the first piece of land in Hong Kong to be designated legally as mainland Chinese territory.

Reports have emerged of travellers going into mainland China having their phones searched for videos and photos related to the anti-extradition bill protests, and even have their private messages with friends and family scanned.

Not the only Hongkonger detained

Cheng was not the only one who was detained by mainland Chinese authorities at the immigration customs.

Several accounts of Hongkongers being detained while passing through customs were posted on social media.

Most were held for a few hours to a day.

In one particular case, an 18-year-old protester was detained at customs when he was found to have an “anti-extradition bill” sign in his bag.

He has since returned to Hong Kong safely.

In another alleged case of detention, a Hong Kong person was detained after being found to have a photo of the protests.

Top image via Silk Road Economic Development Research Center