Two men and a middle-aged couple may hold vital clues to a firebomb attack on a house in which a woman and her nephew were killed.
Gardai said they want to speak to the men who were seen separately in the Rope Walk area of Blackrock, Cork, on Easter Sunday morning, around the time of the incident.
One was wearing a hoodie with the hood pulled over his head and the other was not wearing any clothes on his top half.
Both were seen in the Blackrock area between 2am and 3am on Sunday.
Helena O'Dwyer, 25, and her five-year-old nephew, Ryan, died at the family home in Nutley Avenue, Mahon, a suburb of Cork city, following the arson attack.
Relatives claim the young woman had received death threats in the fortnight before the incident.
A 22-year-old man arrested over the deaths was released without charge but it is understood he has not returned to the area in Mahon where he had been living.
Investigating gardai said they are also trying to trace a couple who were walking along Nutley Road towards Ringmahon Road at about 3am.
Detectives would also like to contact the driver and passengers of a silver or light-coloured Toyota Avensis estate seen in the Blackrock Road/Convent Avenue area at approximately 2.50am. It may have been a taxi or hackney cab.
Gardai also want to analyse mobile phone or video footage of the fire recorded by locals.