A young man was described as being in a critical condition in hospital on Monday night after an assault in Co Meath.
Gardaí have appealed for witnesses following an incident at a residential property in the village of Ballivor on Monday.
Shortly after 7am on Monday, gardaí and emergency services responded to an incident at the property.
A Garda statement said a man in his 20s sustained serious injuries and was taken to Mullingar hospital for treatment before being transferred to Beaumont Hospital in Dublin.
A man in his 40s was subsequently arrested in connection with the investigation and was being detained on Monday night under Section 4 of the Criminal Justice Act. He may be questioned for 24 hours.
The Garda Technical Bureau has conducted a full technical examination of the scene and a senior investigating officer has been appointed to lead the investigation from the incident room at Trim Garda station.
An Garda Síochána appealed to anyone who witnessed the incident to contact Trim Garda station on (046) 9486140 or the Garda Confidential Line on 1800 666 111. Anyone with camera footage, including motorists with dashcam footage, that could help the investigation is asked to make it available.