A number of people were arrested in Galway last night on public order offences.
The arrests coincide with the city's 'Unofficial Rag Week', which began last year after students in GMIT and NUI Galway voted to scrap Rag Week.
Videos have been uploaded to YouTube of last night's events outside Supermac's in Eyre Square. One video shows a large crowd of people shouting while some people try to climb posts.
President of NUI Galway Students' Union Paul Curley said he is confident none of those arrested are Galway students.
"I'm in town now and I'm watching two full bus loads of people come in. I've seen on Facebook that people from all around the country are coming to Galway for this. There are supposed to be buses coming from Letterkenny, Kildare, Limerick and Athlone," he said.
"Of course it worries me, but it's got nothing to do with the students' union or the university."
Mr Curley said he has not received any complaints for residents yet.
Today is expected to see similar events, as this would have been Rag Week's 'Donegal Tuesday', where jersey-clad revellers traditionally take part in a day-long drinking session.
Last year, which was Galway's first unofficial Rag Week, saw thousands of students begin drinking at 10am. GMIT Students' Union President Joe O'Connor said they are preparing themselves for the day.
"Even when the students' unions were involved in Rag week, we never had a role is this event. We have student patrols taking place during the day, which we usually reserve for the night," he said.
"There is a history of students from all around the country coming to Galway for Rag week and with social media and people sharing events, it's difficult to move away from that kind of culture."
A spokeswoman for NUI Galway said students involved in anti-social behaviour will meet disciplinary action.
The University condemns unequivocally any anti-social behaviour by its students. As and when individuals concerned in such behaviour are identified as NUI Galway students, the University has and will continue to deal with them by means of the disciplinary process as outlined in the student code of conduct," she said.
"The University brings to the attention of all of its students, on a regular basis, their obligations, and the possible sanctions which can be applied, under the Code of Conduct."