Authorities across China are cracking down on thousands of college students who took part in mass night-cycling events that commentators said could be seen as a new form of protest against the ruling Chinese Communist Party.

The police department in Henan’s Zhengzhou city issued a warning to students on Nov. 9, following a mass “night ride to Kaifeng” by thousands of young people a day earlier, as a social media video about riding to the city in search of dumplings spawned dozens of copycat outings, eventually expanding to a mass cycle ride that some observers said left the authorities rattled, concerned that it could turn into a political protest like the “white paper” movement two years ago, or Halloween in Shanghai.