A man and woman are being questioned over an arson attack on a house in which a five-year-old girl died.
The woman, in her 30s and the second suspect arrested, was detained in Boyle, Co Roscommon.
The man, detained on Wednesday, remains in custody.
Marie Connolly was found dead in an upstairs bedroom of her father Richard's home in the town in the early hours of Monday.
Her mother Teresa Keane had given birth to twin girls the previous weekend.
Mr Connolly had been looking after the five-year-old and her two sisters Lauren, aged eight and Naomi aged six, who survived the fire.
Both the man and woman were being quizzed in Boyle Garda Station.
Gardai believe the fire was started deliberately.