The State Administration for Industry and Commerce (SAIC) announced last month that it was investigating Microsoft over its Windows operating system -- which is used on the vast majority of computers in China -- and the Office suite of programmes.
Zhang Mao, head and Communist Party chief of the SAIC, told a news conference in Beijing that Microsoft had failed fully to disclose information about its software.
He added the agency, one of the government bodies which enforces China's anti-monopoly law, was also looking into "issues" with Microsoft's media player and browser, according to a transcript posted online.
The European Commission fined it USD 731 million in March last year for failing to offer users browser choices beyond its own Internet Explorer.
"Through repeated contact with Microsoft, their top-level executives have shown respect for China's laws, (and) cooperated with China's anti-monopoly investigation," Zhang said.
Microsoft has said it seeks to comply with Chinese law. Its comments came after the official announcement of the investigation, which included raids on its offices in the country.
In May, China also banned the use of Microsoft's Windows 8 operating system on all new government computers, as reports alleging security concerns circulated.
China -- which is embroiled in a long-running cyberspying row with the US -- is planning to introduce a homegrown operating system as early as October to reduce the country's reliance on Microsoft, the official China Daily newspaper reported today.
The Microsoft probe comes as foreign firms doing business in the huge Chinese market face apparent greater scrutiny.