Detectives investigating a residential fire in which a woman and two children died have arrested their neighbours on suspicion of murder.
The victims - a 20-year-old woman, a boy aged four and a two-year-old girl - died after the blaze broke out in their first-floor flat in Maes Y Groes, Prestatyn, a North Wales Police spokeswoman said.
She added that the arrested pair live underneath them on the ground floor and were a man, aged 45, and a woman, aged 42.
The force said the female victim was related to the two children but was not their mother.
The dead woman's 15-month-old baby boy is in a critical condition in hospital and her 23-year-old boyfriend is also in hospital being treated for serious injuries.
The man is not related to the two dead children, North Wales Police said.
Detective Superintendent John Chapman said: "We would appeal for anyone who may have seen anything suspicious in the Maes y Groes area of Prestatyn yesterday evening to get in contact as soon as possible by calling us on 101.
"We are deploying family liaison officers to work closely with the next of kin at this difficult time.
"There is a team of dedicated officers working on specific lines of inquiry in relation to this incident."
Firefighters were called to the scene at 10pm on Friday night and recovered the five people. A joint investigation was launched by North Wales Fire and Rescue Service and North Wales Police.