Chinese internet giants Tencent, Baidu and Sina Weibo are under investigation for potential cyber-security violations, the mainland’s office for cyberspace administration said on Friday.

According to earlier investigations, the social media platforms of these companies — WeChat, Tieba and Weibo respectively — have users spreading “violent, terror, false, rumored, and pornographic information that damages national and public security [in addition to] disrupting social order,” the office said in a Mandarin notice on its website.

The platforms are “suspected of violating cyber-security laws and did not fulfill duties to manage information published by their users,” the website continued.

Tencent shares in Hong Kong were in the red following the news. The stock was down more than 2 percent following earlier losses of around 4 percent.

Baidu and Sina trade in New York and investors will be watching for any reaction at the U.S. market open.

CNBC’s Barry Huang contributed to this report.