WEST Yorkshire's Chief Constable has said it would be "foolish" for him to speculate on the background to the deaths of a family of four found dead on a bed in their fire-damaged house.

Sir Norman Bettison said investigations into the "background to the motivation" behind the deaths of Richard and Clair Smith and their sons Ben, nine, and Aaron, one, were continuing.

It appears Smith stabbed his wife and children before setting light to the main bedroom of their detached home in Pudsey, near Leeds, and killing himself by smoke inhalation.

Asked about how this could have happened, Sir Norman told BBC Radio Leeds: "It would be foolish for me to speculate at this stage.

"That investigation will take the course it needs to take in order to provide the coroner with all the information that he needs to hold an inquest that allows him to find a conclusion."

He said: "It’s a real tragedy that something like this could happen in a place like Pudsey that expects to get up, go about its business, get the kids off to school, come home, watch a bit of television. Then for something like this to happen in the midst of Pudsey is a tragedy for all concerned."

Sir Norman said: "What we think has happened is that there have been a number of murders and there’s then been a subsequent suicide. We’re investigating the circumstances of that to try and be clear about precise times and what precisely happened and the background to the motivation that drove the incident in the first place."

Sir Norman’s comments follow statements by his senior detectives who stressed they cannot comment on possible motivations for the killings, including reports Smith had recently started an affair with another woman.

It is thought there is no obvious trigger for Smith’s actions.

Police have said the family were last seen at 11pm on Friday night when they left a Christmas party at Pudsey St Lawrence Cricket Club by taxi.

Detective Superintendent Paul Taylor, who is leading the inquiry, 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."

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.

Officers confirmed Smith, 37, died from smoke inhalation.

They said Mrs Smith, 36, 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.

Tributes have continued to be left at the modern three-bedroomed house on Sheridan Way where the Smiths had only lived for a few months.

Relatives have described them as a "perfect family".

Friends said Smith worked for a shopfitting firm as a designer and was a coach for a local football club.

They said the family appeared to have no problems and could not understand what had happened.

Greenside Primary headteacher Janet Howard said it was a "tragic loss" which affected the whole community.

She said: "Ben was a wonderful, bright pupil who thoroughly enjoyed coming to school.

"He loved to help others, was a member of our school council and was a really popular boy, not just with his friends but across the whole school."

Mrs Smith’s parents, Alan and Norma Robinson, have said: "Clair was an exceptional person, loving and caring to everyone.

"She was a loving mum, her children were her life, and everything centred around her family and home.

"She was our daughter and our best pal. We cannot imagine what caused this tragedy."