Chinese authorities are claiming that Microsoft has yet to fully comply with the government's anti-monopoly investigation, and is demanding more information about its media player and Web browser distribution.
"Information relating to Microsoft's suspected Windows and Office software has not been fully open," said Zhang Mao, the head of China's State Administration for Industry and Commerce (SAIC), at a press conference.
The antitrust regulator has been investigating Microsoft on an industry complaint related to compatibility and bundling issues with the company's Windows and Office software. Although the regulator has to yet elaborate on the specific problems, SAIC started raiding Microsoft offices in China last month, as part of its probe.
Despite SAIC's claim that Microsoft is still withholding information, Zhang added that the U.S. company has expressed it will respect Chinese laws and cooperate with authorities in their investigation. He offered no further information.
Microsoft did not immediately comment. But the company has said in the past it is willing to answer the government's questions.
Like in other parts of the world, Windows is still the top PC operating system in China, with a 90 percent share, according to StatCounter. About 40 percent of those users are still on Windows XP, an operating system that Microsoft officially retired earlier this year, ending its support for security updates.
Recently, the Chinese government has been showing signs it wants to curb Microsoft's influence. In May, the country banned government purchases of Windows 8 devices, with a state-controlled publication stating it was because of security concerns.
SAIC's investigation comes as China has been opening other anti-monopoly probes against foreign companies, including car makers and U.S. chip vendor Qualcomm. In Qualcomm's case, the company has allegedly been overcharging clients when licensing its patents.
Earlier this month, SAIC also warned in an online notice that Microsoft would need to follow China's law, and not block its investigation.