A man in his 30s was arrested in Co Sligo this morning in connection with the fatal house fire in Boyle, Co Roscommon last week in which a five-year-old girl died.
It is the third arrest in connection with the investigation.
He is being held at Boyle Garda station under Section 4 of the Criminal Justice Act. A man and a woman arrested last week have been released without charge.
Marie Connolly was killed in the suspected arson attack at her father's house on October 3rd, a day after her mother gave birth to twins.
She was found dead in an upstairs bedroom of the home after the blaze ripped through the terraced home in the middle of the night.
Her father Richard had been looking after her and her two sisters Lauren (8) and Naomi (6), who survived the fire.
The 27-year-old is believed to have leapt from a first floor window with the older girls in his arms.
Marie's mother Teresa Keane, Mr Connolly's former partner, gave birth to twin girls the previous day.