The man who died in custody at Dundalk Garda Station on Thursday night was arrested twice as part of the investigation into the disappearance of Ciara Breen, it has been reported.
Liam Mullen (55) was detained in the station on Thursday evening at 8.30pm.
It is believed he became ill at around 10pm and a doctor was called for. Despite efforts by the doctor to resuscitate him, Mullen was pronounced dead later that evening.
An investigation has been launched by the Garda Siochana Ombudsman Commission (GSOC).