Microsoft has revealed that Chinese authorities have just visited its four offices in the country.

Officials from China's State Administration for Industry & Commerce, the agency that enforces business regulations, paid unannounced visits to Microsoft's offices in Shanghai, Beijing, Chengdu and Guangzhou. The authorities were said to have given no reason for their sudden visits.

"There was a visit from government officials to our offices," Joanna Li, a spokeswoman for Microsoft, said. "Given the sensitivity of the issue, I can't say anymore."

In a statement, Li said that they were pleased to answer the questions of Chinese authorities. 

The visits are a bad sign for Microsoft. Chinese officials have recently gotten into the habit of targeting multinational firms, and it seems that the company is the newest target up for increased scrutiny. In an authoritarian country like China, increased scrutiny means legal troubles and weaker sales. In an interview, a source close to the company said that the visits are probably the early stages of an antitrust investigation. 

Last week, the country's National Development Reform and Commission announced that it was looking into charging Qualcomm for antitrust violations. The agency accused the company of creating a monopoly on the Chinese mobile devices chips market, which it used to overcharge consumers in the country.

Technology firms have particularly been targeted by the country's authorities after revelations from NSA whistleblower Edward Snowden. In his leaked documents, Snowden outlined how US intelligence agencies conducted surveillance through American technology firms. 

One of the biggest casualties of increased scrutiny from Chinese authorities is Google. Last June, days before the 25th anniversary of the Tiananmen Square Massacre, the company's search engine was rendered inaccessible for over a month. The ban also covered other Google services such as Gmail, Google Scholar and Google Books. Google websites for specific countries, such as Google France at google.fr, were also blocked. Meanwhile, YouTube has been banned in the country for years.

This is not the first time that Microsoft has attracted the unwanted attention of Chinese authorities. Last May, authorities prohibited the use of the Windows 8 operating system on government computers due to security concerns.