The detention by Chinese authorities of a British corporate investigator and his American wife in the wake of a corruption probe into pharmaceutical giant GlaxoSmithKline has had a chilling effect on other risk consultants working in China.

It is unclear why Peter Humphrey and Yu Yingzeng, whose firm ChinaWhys has done work for GSK and other drugmakers, were detained. But corporate investigators said they were concerned about the repercussions for the industry.

Multi-nationals, banks and investors rely on corporate investigators for information about potential partners and investments in China, where a lack of transparency is a hurdle to doing business. Restrictions in the flow of such background information could potentially leave foreign investors exposed to greater risk in the world’s second-largest economy.

British diplomats have said they were giving consular assistance to a Briton detained in Shanghai but have declined to provide further details. US diplomats have said the same thing about a detained American.

Some investigators, worried that they may be under surveillance, have scaled back their use of e-mail. Some have declined to speak to reporters over the phone, afraid that authorities were listening in to their conversations.

Several investigators said that they had become more cautious about which projects to accept, avoiding any the Government might see as sensitive.

Investigators said they had also heard of people requesting reassignment to Hong Kong, which has a separate legal system to mainland China. These movements could not be confirmed.

GSK is in crisis in China after police this month accused it of funnelling up to $489 million to travel agencies to facilitate bribes to doctors and officials.