It is believed little Ryan Busa was mauled to death by the family’s pet Alsatian dog.
Despite being rushed to the Royal Belfast Hospital for Sick Children, young Ryan died of his injuries.
A post mortem examination is due to take place today to determine the cause of death.
A 38 year old man remains in custody assisting police with their enquiries.
The officer leading the investigation Detective Inspector Darren McCartney said: “I am appealing for anyone in the local community who has any information that can assist with the investigation to contact detectives by calling 101, quoting reference number 848 15/10/17.”