The Chinese body in charge of antitrust matters, the State Administration for Industry and Commerce (SAIC), has confirmed that Microsoft has 20 days to provide answers to a list of questions.
These cover the relationship (or as Reuters puts it, compatibility) between Microsoft's ubiquitous Windows operating system and its equally popular Office operating system.
SAIC questioned David Chen, Microsoft' Vice president, and hinted that it suspects that the world's largest software company did not disclose all the information it needs to about the two products.
Microsoft said it was "serious about complying with China's laws and committed to addressing SAIC's questions and concerns".
As for the SAIC, it confirmed that a "special investigation team conducted an anti-monopoly investigation inquiry with Microsoft Vice President Chen Shi (David Chen), and required that Microsoft make a written explanation within 20 days".
Why exactly SAIC is investigating Microsoft over Windows and Office remains unclear as the two can be used independently from each other.
Past anti-competitive investigations focused mostly on how Microsoft tied its browser, Internet Explorer, and media player, Windows media Player, with Windows.