BEIJING, July 29  -- China's market regulator has launched an anti-monopoly investigation into Microsoft Corp's business in the Chinese mainland, it confirmed on Tuesday.

The State Administration for Industry & Commerce (SAIC) said the investigation involved Microsoft China Co., Ltd, and three of its branches in Shanghai, Guangzhou and Chengdu. The administration said the firm had not fully disclosed anti-competition information about its Windows operating system and Microsoft Office application as required.

Inspectors are investigating a Microsoft vice president and senior managers, and have made copies of the firm's financial statements and contracts, the SAIC said in a statement on its website.

The administration has seized documents, e-mails and other data from Microsoft's computers and servers. It has not been able to complete its investigation because key personnel of Microsoft are not in China or cannot be contacted, according to the statement.

In June last year, the SAIC investigated complaints from enterprises that Microsoft had used tie-in sales and verification codes in its Windows operating system and Microsoft Office application, causing software incompatibility issues.

Microsoft failed to fully disclose information as required by the SAIC about such complaints in its reports submitted to the regulator, and may have breached China's Anti-Monopoly Law, the statement said.

Under the law, companies or individuals should not abuse their market dominance to exclude or restrict competition and should be supervised by the public.

The SAIC can require a suspected violator to submit relevant documents or materials during investigations.

The administration said a preliminary inspection had not removed suspicions related to Microsoft's alleged anti-competitive activities.

Microsoft's lawyers were present during the inspection, according to the SAIC.