The bodies of a mother and her two boys, aged eight and nine, have been discovered in a house in Castledaly, a small village just outside Athlone in Co Westmeath.
The father of the family, who is in his 30s, was also seriously injured.
Detectives are currently trying to determine how the three people died and what exactly happened prior to their deaths.
The scene has been preserved and the State Pathologist has been called to carry out post mortems.