Two men were taken to the Mater Hospital in Dublin after they were injured during a disturbance at a property on Ormond Quay.
Gardaí responded to the incident shortly before 1pm on Saturday.
Gardaí at Store Street say they are investigating all the circumstances around the incident, which is understood to have involved the forcible removal of a number of people from the building by a group of men.
Gardaí and the Public Order Unit were also called to an address at Ormond Quay last night following reports of a disturbance there shortly before 10.30pm.
The disturbance was brought under control and gardaí say a number of men who had gathered there were stopped and searched.
One man in his 40s was arrested for public order offences but has since been released without charge.
A number of items which gardaí say were of evidential value were seized yesterday and gardaí say investigations into both incidents are ongoing.
In a statement, Aubrey McCarthy, chair and founder of Tiglin, a charity which aims to help people overcome homelessness, said:
“Tiglin’s homeless outreach team was made aware of a violent disturbance involving a group of men on Ormond Quay.
“Some of the men were seen using sticks and fire extinguishers to harm each other. This kind of violence is completely unacceptable and cannot be tolerated under any circumstances.
“Homelessness is at an all-time high but it is crucial that we all work together, regardless of nationality, to ensure the safety and wellbeing of everyone in our community.”
