Gardai said they are investigating “all the circumstances” of the fire at Castleview Park in Edenderry.
An Garda Siochana said: “The body of an adult person has been discovered inside the premises.
“A post-mortem will be conducted to determine the cause of death, which will determine the course of any Garda investigation.”
The scene of the house fire in Edenderry in December (PA)
The scene has been preserved for forensic examination and gardai are appealing for any person with any information on the fire to contact them.
The incident occurred at the same house where four-year-old Tadhg Farrell and his great-aunt Mary Holt were murdered in December 2025.
The young boy’s grandmother also received hospital treatment for serious burn injuries in that first blaze.
A man in his late 20s who had been detained on suspicion of murder was released without charge in January.