A veteran Hong Kong policeman has been arrested for allegedly aiding and abetting the ringleader of a prostitution racket who was staying in the city illegally and faces suspension from duty, the Post has learned.

Crime-squad officers were also investigating whether the constable, 46, tipped off the syndicate so it could avoid anti-vice operations, a source familiar with the case said on Thursday.

The officer worked at Tsim Sha Tsui Police Station while the syndicate operated in hotels in the same district with sex workers from Russia, Japan and mainland China.

The alleged mastermind was a 33-year-old woman who entered the city illegally from the mainland, according to the source. She was arrested on Saturday.

The constable was detained on Wednesday night when investigators raided his flat in police quarters in Kowloon Bay.

Police began investigating the syndicate in October, following the arrest of a Japanese AV (adult video) actress in another operation. The 27-year-old was intercepted in a Tsim Sha Tsui hotel on October 17.

The investigation revealed that the ring operated across five hotels, including five-star establishments, in the Tsim Sha Tsui entertainment district, according to the force.

Four sex workers from Russia and Japan were among 17 women arrested in a series of raids at five hotels on Monday last week. The syndicate also used a hotel room as its operational centre which was discovered in the raids.

The alleged mastermind had managed to leave the operational centre in the Kimberley Hotel before the raids.

On Thursday last week, officers arrested a 40-year-old man on suspicion of aiding and abetting an offender. He was later released on bail, pending further investigation.

Two days later, the alleged ringleader was picked up in a Causeway Bay hotel room. Officers seized HK$150,000 (US$19,271), believed to be the proceeds of crime, from her room.

The constable was identified in the investigation, which showed he allegedly met the alleged ringleader when she was on the run, according to the source.

The source said the woman seemed to know how to elude police surveillance and it was possible the constable had helped her. He added the pair had known each other for months.

“We don’t rule out the possibility that the constable will be arrested for other offences,” the source said, adding the officer was likely to be released on bail pending further investigation but would be suspended from duty.

As of Thursday night, he was still being held for questioning and had not been charged.

Detectives from the Kowloon West regional crime unit are investigating the case.

Without providing details, a police spokesman said a 46-year-old officer had been arrested in Ngau Tau Kok on Wednesday for aiding and abetting, counselling and procuring an illegal immigrant to remain in Hong Kong without the authority of the director of immigration.