Male tourists to Hong Kong are being targeted by sex workers who rob them after lacing their drinks with drugs, police say.

Forty-four foreign men have reported being robbed this way since 2004, usually in Hong Kong's red-light Wan Chai district, police said.

However, they said the number may be higher as many incidents go unreported due to embarrassment or because the victims have left Hong Kong before the crime is noticed.

A police spokesman told the Sunday Morning Post that they believed the culprits use "some kind of date-rape drug".

In most cases the victims are approached by sex workers in bars. Some claim to remember very little and only notice unexplained cash withdrawals from ATMs later when they receive bank statements.

Others awake disorientated in short-stay hotel rooms with valuables and cash missing.

In 2003, a senior Finnish policeman died of a heart attack in Hong Kong's Island Shangri-la hotel after being drugged. The Chinese prostitute suspected of giving him the drug was never traced.

Last year, British Airways banned staff from visiting a popular Wan Chai bar after several crew members were suspected of being given date-rape drugs in drinks, claimed the report in the Sunday Morning Post.

Meanwhile police are continuing to investigate the possible poisoning deaths of two Americans at the Grand Hyatt hotel in the Wan Chai district over a week ago.

Reports said the two men, identified only as Paul, 45, and Richard, 51, had been to a nightclub before returning to their room with two women.

The men's slumped bodies were discovered the next day by cleaning staff.

Police have yet to say what caused the men's deaths, although they have not ruled out that they were drugged.

The Standard newspaper reported that a mixture of cocaine and heroin was found in their blood, but police have refused to comment, saying toxicology tests were continuing.

A Filipino woman arrested shortly after the bodies were found has been released, but will appear in court on charges of violating her visa by moonlighting as a prostitute, a police spokesman said.

DPA/AP