A man was being questioned by police on Tuesday night following the sudden death of a baby in Co Armagh.
It's understood the 11-month-old boy was pronounced dead following an overnight incident at his Market Street home in the village of Keady.
He was named in a death notice as Hunter Patrick McGleenan.
It's believed the child's mother, Nicole McGleenan (27), was not at home with him on Monday night as she was visiting an ill relative and only discovered yesterday morning that her baby was not breathing or moving.
The child was later pronounced dead at Craigavon Area Hospital.
While sources have claimed that the baby may have been dropped, the PSNI said that a post-mortem will take place to determine the exact cause of death.
A 31-year-old man was arrested in Craigavon following the incident. He is understood to be the partner of Ms McGleenan and is believed to have been caring for her infant son at the time.
He was last night being questioned by detectives at Banbridge Police Station.
The PSNI said that an investigation has been launched following the incident.
There are no further details at this stage.
Officers remained at the family home in the centre of the south Armagh village last night as forensics officers removed items from the property including a pram, clothing and a laptop.
Neighbours were too shocked to speak publicly last night but reported that there had been police activity at the small terraced house for most of yesterday.
Ulster Unionist councillor Sam Nicholson was among those who expressed his sadness at the tragedy.
He said: "This is truly shocking news within our community and our thoughts are with the child's parents and family at this terrible time. The loss of an infant is an awful thing to have to go through.
"I don't know how they will ever get over it.
"It is a devastating loss especially happening so close to Christmas, which is a family time."
Sinn Fein MLA Cathal Boylan, who is understood to be a friend of the baby's family, added: "I have now spoken to a family member and they are all in deep shock.
"They have asked for privacy as they try to come to terms with this unfathomable tragedy. We shall of course keep them in our prayers."