Police in Shanghai have detained a British fraud investigator who had worked with pharmaceutical firm GlaxoSmithKline (GSK), which is being probed by China for alleged bribery, a report said Sunday.

Peter Humphrey, managing director of a firm which investigates accounting fraud for multinational businesses operating in China, was arrested earlier this month, Dow Jones Newswires cited sources as saying.

Humphrey's clients included GSK, the sources said. An ongoing Chinese bribery investigation into the pharmaceutical giant has seen four of the company's top executives in China arrested, while its British finance director has been barred from leaving the country.

A spokesman for the firm declined to confirm if it had employed Humphrey as a contractor, Dow Jones said.

Police in Shanghai could not be immediately reached for comment on Sunday.

A spokesman for Britain's embassy in Beijing told AFP: "We are aware of the arrest of a British national in Shanghai, China on the 10th of July. We are providing consular assistance to the family."

It is unclear where Humphrey is being held, whether he has been charged, or has retained a lawyer, Dow Jones reported.

Humphrey, a former reporter who speaks fluent Mandarin, founded ChinaWhys Co., a Hong Kong-based investigation firm with his wife, a specialist in forensic accounting, the report said.

China has seen "a tightening" of access to the kinds of information needed to conduct fraud investigations, the China chief of one due-diligence firm was quoted as saying on Saturday.

GSK has said it is cooperating with China's investigation, and that bribery is against its policies.

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