AstraZeneca's China president Leon Wang, who was detained last month by Chinese authorities, is in touch with a lawyer but the company has very little information about the case, its CEO said on Tuesday.

Leon Wang, executive vice president in charge of China and the broader Asian region, is being detained while the Chinese government is probing AstraZeneca employees, the drugmaker says.

While it remains unclear why AstraZeneca China President Leon Wang has been detained, news of his arrest comes just days after it was reported that he was under investigation for alleged medical insurance fraud in the country.

AstraZeneca said on Wednesday its China president Leon Wang had been detained by Chinese authorities and, although it did not know the reason, it did not believe it was linked to a large health insurance fraud case involving the company.

Shares in AstraZeneca were down 1.3 percent in midday deals on London's top-tier FTSE 100 index, which was trading one percent lower overall. Its shares fell sharply when reports of Wang's detention emerged earlier this month, wiping billions of dollars off its valuation.

China's investigation of AstraZeneca's top executive in the country is raising questions about the company's tactics there.

AstraZeneca's CEO said on Tuesday that the company's China president Leon Wang, who last month was detained by Chinese authorities, has a lawyer he is in touch with, but "we have no information as a company".