A man (18) who was arrested in relation to the alleged assault of a 10-week-old baby, has been released without charge.
A file will now be prepared for the information of the Director of Public Prosecutions.
The suspect was arrested in Dublin last night and was questioned at Dundalk garda station. The baby remained in a critical condition last night and there is grave fears that she will not survive.
It's believed the arrested teenager is known to the baby girl. It is understood senior officers made the decision to arrest the suspect when they became "dubious" of an account the young man gave investigating gardaí about last Monday's suspected assault in Ardee, Co Louth.
The man was arrested on suspicion of assault causing serious harm to the child.
The baby girl was clinging to life last night on a ventilator at Temple Street Children's Hospital in Dublin.
She suffered severe head injuries and other broken bones during the incident.
Sources said officers were probing whether she might have been the victim of an assault.
It's understood gardaí are studying CCTV and examining items recovered in searches in Ardee. Sources said specialist officers would also reinterview a number of people.
The heartbroken family of the baby remained at the hospital last night. Sources said gardaí were treating the case as "extremely sensitive and difficult". The investigation is being led out of Ardee garda station by Superintendent Fergus Treanor.
The baby girl was transferred to Temple Street after being presented at Our Lady of Lourdes Hospital in Drogheda. The baby is the child of teenage Irish parents and had been living in an apartment in Ardee with them.