The Lucknow University administration on Wednesday said that a group of people claiming to be Samajwadi Party workers attacked faculty members on its campus. The proctor and more than 12 staff members and guards sustained injuries during the attack, Vice Chancellor SP Singh told reporters.

Officials said the campus will remain closed until further notice. “All those involved in the incident were not Lucknow University students,” Singh said.

Police said they have arrested three people in connection with the case, PTI reported. “We are awaiting a complaint from the university administration,” Superintendent of Police Harendra Kumar said.

On Tuesday, more than 20 students who had allegedly waved black flags at Uttar Pradesh Chief Minister Adityanath’s convoy near the campus in June 2017 claimed to have been unfairly denied admission to postgraduate courses of their choice, Hindustan Times reported. Most of the protesting students are believed to be members of the left-wing All India Students’ Association and the Samajwadi Party’s student wing.

The university, however, contradicted their claims. “We have the written undertaking of candidates whose expulsion was revoked when they agreed not to enroll in any other course in future,” Lucknow University spokesperson NK Pandey told the newspaper. “The candidates denied admission include those who were involved in repeated incidents of indiscipline and were issued notices for vandalising mess property, holding officials hostage, showing black flags to chief minister and staging protests.”