A smartphone showing the Baidu Browser application is seen in this picture illustration, February 22, 2016. [Photo/Agencies]

BEIJING - Chinese search engine giant Baidu is being investigated for allegedly advertising gambling websites, the Cyberspace Administration of China (CAC) confirmed Tuesday.

The CAC Beijing branch is responsible for the probe, said a spokesperson of the CAC, the country's cyberspace regulator.

Reports this week revealed that Baidu returned search results that included ads for gambling websites in its commercial section.

The report also said that the names and information of some legal entities had been appropriated to make the gambling websites appear to be verified companies. It was not disclosed whether Baidu knowingly allowed such practice.

The CAC called on Baidu and other search engines to observe a recent regulation on search services, as it is their social obligation to stop the spread of illegal content.

This is not the first time Baidu has been under fire due to its business model. Earlier in May, it was implicated in a controversial cancer treatment case due to its advertisement model to "pay for higher ranking," which was not properly supervised.