China's State Administration for Industry & Commerce (SAIC) is conducting an anti-monopoly investigation into Microsoft because the firm has not fully disclosed information about its Windows operating system and Microsoft Office software. The Chinese regulator said on Tuesday that it was investigating a Microsoft vice president and senior managers, and has made copies of the firm's financial statements and contracts.

Microsoft has been suspected of violating China's anti-monopoly law since June last year in relation to problems with compatibility, bundling and document authentication, SAIS said in a statement.

Yesterday, officials from the agency raided Microsoft offices in Beijing, Shanghai, Guangzhou and Chengdu.

Microsoft said on Monday it was "happy to answer the government's questions", a statement it repeated after the announcement from the regulator on Tuesday.