The person under investigation is Frederic Choi, head of the police National Security Department that was set up last year after Beijing decided to impose a new set of laws on Hong Kong against subversion, secession, collusion and terrorism.

Commissioner of Police Chris Tang said Choi has been put on leave during the investigation. Tang provided few details about the raid.

“I think the work of the National Security Department will not be affected by the investigation of an allegation against an individual officer, because we are a team and work as a team,” Tang said at a news conference.

While operating an unlicensed massage business is an offense that can result in up to six months’ jail and a 50,000 Hong Kong dollar ($6,440) fine, patronizing such establishments is not illegal.

The National Security Department was set up following the implementation of the new security law last year, which came as Beijing aimed to silence dissent in the semi-autonomous territory following months of anti-government protests.

Choi, who is also a senior assistant commissioner, joined the city’s police force in 1995. In February, he received an award for his contributions to national security from the city’s leader, Carrie Lam.

He was sanctioned by the U.S. earlier this year together with six other national security officers for undermining the autonomy of Hong Kong, a former British colony that was handed over to Beijing in 1997.