GlaxoSmithKline, Britain's biggest pharmaceuticals firm, says it doesn't know why police in China have been investigating it for six days.
Senior executives at Glaxo China are suspected of "economic crimes", according to an official blog post by police in Changsha in Hunan Province. But a Glaxo spokesman said: "We're still unclear about the precise nature of this investigation."
Separately, officials in Beijing are investigating potential price-fixing among drugmakers, including GlaxoSmithKline as well as its rivals Merck, Novartis and Baxter.
China's National Development and Reform Commission said it will investigate 27 companies on costs and 33 on pricing.
This is the second Chinese government investigation into pricing by foreign firms to be revealed this week. On Tuesday, several baby milk producers in China said they were being investigated by the NDRC. In response today, Nestle and Danone said they would cut prices of some infant milk formulas in the country.