Police said on Tuesday that a Chinese University student is wanted in connection with an alleged attack earlier this month by a group of people on campus security guards.
The force called on the student, who wasn't named, as well as "other assailants" to turn themselves in as soon as possible, so that "people who care about them won't commit wrong acts in order to protect them."
The appeal followed the arrests on Monday of three other students on suspicion of unlawful assembly and assault over the incident on January 11.
Another student was arrested on the day itself, with all those held so far male and aged between 19 and 22.
Detective superintendent Chen Chi-cheong alleged that the suspects were trying to force the university to stop implementing identity checks at campus entrances.
"The Chinese University is not above the law. The police won't tolerate people trying to hide their illegal acts through the special environment at the campus," he said.
Chen also decided to use the press conference to give his views on the alleged incident as an alumnus of the university.
He made clear it was in this capacity that he was speaking when he described what had happened as "triad-like methods to bully and attack the security guards".
Chen then criticised the university's student union, accusing it of attempting to play down the alleged crime as "clashes between students and security guards", saying this was nothing but a "shameless excuse."
Meanwhile, the union expressed regret that the police had once again conducted "mass arrests" of students and entered the campus for investigations.
It confirmed that one of those arrested was the union's leader, Owen Au.
The group accused university management of refusing to deal with problems arising from the introduction of the security guards, condemning them for calling the police.
The January 11 incident is said to have involved a security counter near University MTR Station being damaged, and powder and eggs being thrown at the guards there.