BEIJING - Chinese authorities are investigating 52 more popular websites for spreading violent and pornographic content, following two high-profile probes into Sina.com and Qvod.com.

The websites include online forums, blog services and video websites like tieba.baidu.com, blog.163.com, tudou.com and doc88.com, said a statement issued by the State General Administration of Press and Publication, Radio and Television (SGAPPRT) on Thursday.

They were found to be publishing pornographic and unhealthy content, the statement said. It cited "Chilling Grimm's Fairy Tales," a Japanese adaptation of the classic fairy tales, which minors can easily view online.

If the investigation verifies the malpractice of the websites, the operators will face civil and criminal penalties, the statement said.

This is China's latest move in a campaign to clean up the Internet.

In April, Chinese Internet giant Sina.com was stripped of its online publication license, after articles and videos on the site were confirmed to have contained lewd and pornographic content.

Then in May, Qvod Technology Co., Ltd., a Shenzhen-based provider of Internet video services, was also found guilty of spreading lewd and pornographic content and was stripped of its license to offer paid-for telecommunication services.

According to the SGAPPRT, it has banned 122 online publications and punished 93 websites since the campaign started in April.