A woman who was being questioned by gardaí in Co Mayo in connection with the death of a four-month-old boy has been released without charge.

The woman, who is in her 20s, was arrested yesterday afternoon and detained overnight at Claremorris Garda Station.

A file is being prepared for the Director of Public Prosecutions.

The investigation follows what gardaí are describing as the "sudden and unexplained" death of the baby at the beginning of the year.

He sustained injuries following an incident at a house on 28 December.

He was first taken to Mayo University Hospital in Castlebar and subsequently transferred to Our Lady's Children's Hospital in Dublin, where he died on 1 January.

A post-mortem examination was carried out by the State Pathologist.

While the results are not being released for operational reasons, it is understood the baby had suffered head injuries.