A British man who disappeared shortly before his wife and baby daughter were found murdered at their home in the United States was last night believed to have returned to the UK.

Police investigating the double shooting said they had tracked down 27-year-old Neil Entwistle to a location outside the US and spoken to him several times, although they were still not calling him a suspect.

Mr Entwistle, a former York University student, vanished from the home in Massachusetts, where the bodies of his wife, Rachel, 27, and daughter Lillian Rose were discovered last Sunday night. They had been shot.

Last night, the local District Attorney's office in the US said progress in the case meant they were "slowly but surely" piecing together the puzzle surrounding what happened.

Reports on a radio station in the US said two independent sources showed that Mr Ent-wistle was on a passenger list for a flight from Boston to London on Friday.

On the couple's website, a message from "Matt" in the UK, who said he was Mr Ent-wistle's cousin, said: "As far as I know, his dad collected him as they live in England and he knows no one over there (in America)."

Mrs Entwistle is believed to have been holding Lillian in her arms when they were shot intheir rented home in Hopkinton, Massachusetts.

Local District Attorney Martha Coakley said Mr Entwistle had been out of town since at least Friday.

"He had contacted police at one stage and we have been in touch with him since," she said.

She added: "We are aware of where he is. There are other people that we are interested in talking to.

"I am not going to label him a suspect at this stage. Obviously we have a high level of interest in him."

Last night, a spokeswoman for the District Attorney's office said they were not only interested in talking to Mr Entwistle.

She said: "We are talking to everyone we can. But because they had only lived there for ten days, many of their neighbours don't even know them."

US-born Mrs Entwistle and her baby were found with little to no blood on the bed and no obvious signs of foul play - leading officers at first to think they might have died of carbon monoxide poisoning.

Their bodies were discovered a day after friends and family turned up for a dinner party only to get no reply at the house.

Mrs Entwistle - then Rachel Souza - met her husband at York University, where he studied electronic engineering with business management from 1998 to 2002.

She was in York as a visiting undergraduate from 1999 to 2000 and again to take a teaching qualification between 2001 and 2002.

She and Mr Entwistle, whose family are from Worksop, Nottinghamshire, were members of the university boat club, where they met.

They married in 2003 and moved to the US, shortly after Lillian's birth. Mr Entwistle was looking for a job in the technology field.

They had set up a website with photographs and a message signed from "the happy family".

Yesterday, the site's forum contained pleas for the killer to give himself up and was flooded with tributes from pupils at a school in Redditch, Worcestershire, where Mrs Entwistle had worked.

A spokesman at York University said they had been shocked to hear the news and an old university rowing friend of the couple, John Gibbard, said all sympathies were with the families at "this horrendous time".

Mr Entwistle's father, Cliff, a miner and councillor on Bassetlaw District Council, and his mother, Yvonne, were not available for comment yesterday, having apparently left their Worksop home at 7am.

Neil Entwistle's brother, Russell, was believed to have travelled from his home in Leeds to join his parents in Worksop