Two men have been arrested over a house fire which killed a mother and her four-year-old son in Eastbourne.
Gina Ingles and Milo Ingles-Bailey died in an arson attack at their home in Croxden Way on 10 July 2018, police said.
A 41-year-old man from Hastings was arrested on suspicion of murder and a man, 27, from Eastbourne was arrested on suspicion of conspiracy to murder.
A third man has been interviewed in Portugal.
Miss Ingles's partner Toby Jarrett, 27, was also in the house at the time of the fire, but managed to escape through a first floor window. He sustained serious burn injuries and was taken to hospital for treatment.
Sussex Police officers made the arrests as part of a week of action in the Operation Druffield murder investigation, which relates to the deaths of Miss Ingles, 34, and her son Milo.
Both men arrested were interviewed and later released under investigation.
Detectives travelled to Portugal during the week and interviewed another suspect who is already in prison for an unrelated offence.
Two local men, aged 47 and 23, were previously arrested on suspicion of two counts of murder and one of attempted murder.
The 23-year-old remains released under investigation pending further enquiries while the 47-year-old was released without charge and will face no further action.