More than 1.4 million accounts of 360 Yunpan, a Chinese cloud storage service, have been closed after police received information that the platform has been used to store and trade pornographic materials.
Some of the pictures and movies involved underage sex, China Central Television reported on Tuesday.
Police said people have been selling passwords linked to porn Yunpan accounts on social network platforms, including WeChat.
360 Yunpan said on its Sina Weibo that they would strengthen content selection and establish a mechanism with other companies to jointly control unhealthy content.