A mother and her two sons whose bodies were found in a bedroom at their home had been stabbed, police have confirmed.
Clair Smith, 36, and her sons Ben, nine, and Aaron, one, are thought to have been attacked by the boys' father Richard Smith, 37, who then killed himself.
Police said all four were found dead together on a double bed in the fire-damaged main bedroom of their home in Sheridan Way, Pudsey, near Leeds, on Sunday.
Officers confirmed Richard Smith died from smoke inhalation. They said Mrs Smith died from a single stab wound to her chest, as did baby Aaron. Ben suffered a stab wound to the chest area but died as a result of suffocation.
Detective Superintendent Paul Taylor, of West Yorkshire Police, said Ben's unopened advent calendar was one clue to when the killings happened.
Mr Taylor said the family were last seen at 11pm on Friday night when they left a function at Pudsey St Lawrence Cricket Club by taxi.
The detectives said: "Ben's advent calendar is not opened on the Saturday so we believe something's happened overnight Friday or the early hours of Saturday but, of course, if anybody else has any information that would contradict that we would very much want to hear from them."
Mr Taylor said officers were talking to people who were at the cricket club party but confirmed there had been no reports of any unusual incidents at the function.
The family was found dead after concerned neighbours called at the house on Sunday afternoon followed soon after by police officers. Police have not commented on reports Smith was seen cleaning his car at the weekend.
Mr Taylor said he could not give any further details about how the family died, but repeated his statement that due to the "cause of deaths and other physical evidence found with the scene" he is not looking for anyone else in connection with the deaths.
