Saturday night’s fire claimed the lives of two individuals.
The Taoiseach says the fire in Edenderry in Offaly on Saturday was an attack on society itself.
Gardaí have launched a murder investigation, after 60-year-old Mary Holt and 4-year-old Tadhg Farrell were killed in the blaze.
Officers are appealing to anyone who was in the area on Saturday night to come forward.
Micheál Martin says those responsible will be brought to justice.
Anger is building in Edenderry following the incident.
The investigation suggests the arson attack may be drugs-related.
Honourary Chair of Derry Rovers Football Club, Pat McBride says those behind anti-socail behaviour are responsible:

Fine Gael TD for Offaly John Clendennen says people deserve to feel safe in their own homes.
Orange Wind Alerts Issued As Storm Bram Approaches
Irish Hauliers Threaten Protests Over Toll Discount Dispute
Tributes Paid To Former Fine Gael Midlands Politician
Midlands 103 Launches Joint Christmas Appeal With Simon Community
Woman Facing Life In Prison After Double Midlands Murder
Housing Committee Chair Flags Cost Concerns Over Apartment Fire Safety Scheme
Justice Minister Wants People To Come Forward Over Offaly Arson Attack
New Report Warns Of “Poor Liquidity” As Ireland’s Housing Market Stalls
Laois TD Renews Calls For Updated Wind Farm Guidelines
Midlands Man Laid To Rest Today
Anti-Racism Funding Granted For Offaly And Westmeath Groups
Gardaí Begin Murder Investigation After Child And Woman Dies In Offaly House Fire
Ashling Murphy Murder "Wrongly Accused" Granted Bail Over Theft Charge
Young Boy And Woman Killed In Offaly House Fire
Laois Makeup Artist Warns Of Expired Suncream Dangers
Lynx and Wolves In Ireland Pose Minimal Threat - Offaly Biodiversity
€4.5m Going To Midlands Suckler Farmers
Westmeath Writer Nominated Posthumously For Award
Seven Midlands Hotels Nominated For Gold Medal Hotel Awards