Students and alumni had filled the 1,400-seat Sir Run Run Shaw Hall at the university’s Sha Tin campus for a dialogue session with Tuan.

“Do you know the body search room in San Uk Ling is all dark? Do you know I am not the only one who was subjected to sexual violence?” she said.

She also challenged Tuan to issue a statement to condemn alleged sexual violence by police, removing her mask in front of the university head.

“I am willing to be courageous and take off my mask, would you also be brave and support us, and condemn police violence towards all the people arrested, including Chinese University students?” she said.

In a statement released shortly before midnight on Thursday, police said they were aware of a female student claiming she was sexually assaulted by officers when she was detained at San Uk Ling Holding Centre.

“Police accord high priority to such a serious allegation,” the force stated, adding that its Complaints Against Police Office had not received any case of sexual assault related to the facility.

“We will proactively contact the [woman] and appeal to her to provide concrete evidence so that we can launch a fair fact-finding investigation as soon as possible,” the statement added.

Did police use excessive force or issue a proportional response?

Ng clarified on a radio show on Friday morning that the incident of sexual assault she had described was at Kwai Chung Police Station instead of the holding centre. But she said she was told there were also sexual assaults at the centre.

She said during her stay at the station, a policeman had hit her breasts, and two female officers watched her while she was in the toilet.

Ng said on Friday that she was in fear after the release of the police statement.

“I felt that the police statement was threatening me,” she said. “They said they would contact me directly ... Does it mean that they can catch me again and [detain me] for another 48 hours?”

She added that she had received calls from mainland numbers on her phone since the police statement, and this had not happened before.

Tony Tse Wai-chuen, vice-chairman of the Independent Police Complaints Council, asked people in need to approach the watchdog.

“We hope that those who were treated unfairly or sexually assaulted will make complaints to us. We will follow up,” Tse said on the same radio show on Friday, adding that so far the council had received two complaints related to the holding centre.

Separately, education minister Kevin Yeung Yung-hung said he felt upset after learning about the sexual assault claim by the student. He hoped counselling, which the university was said to offer, would be provided to her soon.

He also asked people with more knowledge on such claims to provide information to police.

How embattled police force is holding the city back from the brink

During the 3½-hour session, Tuan was repeatedly questioned about the support the university provided to students. His replies were often interrupted by angry students who chanted slogans, pointed laser beams, shouted profanities and sang protest songs.

“Why is it so hard [for Tuan] to condemn police brutality?,” a student said, weeping.

Tuan replied that he would issue a statement in a week and condemn what was seen as police’s sexual violence. He attempted to leave the venue but later returned for a two-hour closed-door meeting with students.

According to one participant of the private session, Tuan was told by some tearful students about being beaten with police batons and having their homes searched by officers, while many others said they “could not see a future”, as the president, who turned tearful, said he “really hoped to help students”.

How do Hong Kong’s student protests compare with those worldwide?

Earlier in his opening speech for the dialogue, Tuan said the government should “do more work” to resolve the many deep-rooted problems in a divided society.

“I understand that [students] are feeling emotions such as sadness, distress, fear, anger and also the feeling of powerlessness,” he said. “To be frank, I share these feelings, too.”

Police dismiss accusations of excessive force at Prince Edward MTR station

The law was not applicable on university campuses, he said, without elaborating on whether he was for or against the legislation. He also reiterated his stance of “condemning all kinds of violence”, including police violence.

An alumni member appealed to students to stop using “insulting words towards principal Tuan”. A non-local student asked her fellow schoolmates in Mandarin to “respect other people’s views”. She also raised concerns about non-local students being “attacked” on campus because of their political views.

Other students spoke out against the incident on Sunday when riot police officers entered the university and searched five students who were putting up promotional material. No arrest was made.

He admitted that officers had entered the university, but said the school’s security officers oversaw the situation. He said he hoped similar events “would not happen again”.

Students said they were disappointed by Tuan’s response.

A 21-year-old student surnamed Tsang said he felt “frustrated” by Tuan’s comments, accusing the school official of evading many of the students’ questions. Tsang said Tuan “did not offer anything new” during the session, adding that he had hoped Tuan would promise more concrete actions for the arrested students.

Tuan, who later met the students at an open venue on campus, criticised students for their “disruptive behaviour”.