A Briton whose American wife and child were shot dead in their home has been questioned at the US embassy in London.
The couple moved to the US after their daughter was born
Neil Entwistle, 27, is understood to have returned to his parents' home in Worksop, Notts, after being questioned for four hours on Friday.
He attended the embassy voluntarily to be questioned by detectives, and is not being treated as a suspect.
Rachel Entwistle, 27, and baby Lillian, nine months, were found at their home in Hopkinton, Massachusetts, on Sunday.
A US embassy spokeswoman said it provided the facility for questioning Mr Entwistle at the request of authorities in Massachusetts and in co-operation with British authorities.
"Mr Entwistle is not charged with nor suspected of any federal crime. No embassy personnel are involved in the investigation," she said.
US police had already spoken to Mr Entwistle on the phone following the discovery of the bodies of his wife and child.
The 27-year-old is thought to have left the US before the bodies were discovered under a pile of blankets in a bedroom at their home.
Mrs Entwistle had been shot in the head, Lillian in the body, at some time between last Friday morning and Saturday night.
Mr Entwistle, from Worksop, Nottinghamshire, is believed to have boarded a flight from Boston to London on Friday.
The family had lived at the address for only 10 days.
They were reportedly due to host a dinner party on Saturday night, but when guests arrived, it appeared that no-one was at home.
It has emerged that police only found the bodies on a second visit to the house.
Officers went to the house on Saturday night, after being contacted by Mrs Entwistle's mother and stepfather, but saw only what appeared to be an unmade bed.
It was only when they returned on Sunday that they noticed an odour which suggested there might be bodies in the room, and discovered them under the bedding.
Four US detectives arrived in the UK on Thursday morning after the authorities in Massachusetts revealed they knew of Mr Entwistle's whereabouts and had been in contact with him.
Nottinghamshire Police issued a statement on Thursday night saying Mr Entwistle was not a suspect in the case and was being treated by the US authorities as a "potential witness".
In a statement, District Attorney Martha Coakley, leading the investigation in America, said: "At this time, Neil Entwistle, husband of Rachel and father of Lillian, remains a person of interest in this investigation.
"No one has been ruled in and no one has been ruled out as a suspect in this investigation.
"A person of interest is a person who we believe may have relevant information about the case that we are investigating."
The couple met through a rowing club when Mr Entwistle was studying at the University of York.
They married in 2003 and moved to the US shortly after their daughter was born. Mr Entwistle was said to have been looking for a job in the US.
Mrs Entwistle taught at St Augustine's Catholic School in Redditch, Worcs, between 2002 and 2005.
The couple had a website and it has been flooded with messages and prayers for the family.
Staff at the school where Mrs Entwistle taught have spoken of their "deep sadness" at the news of her, and her daughter's death.
"Rachel was very much liked by all in the school. She was a very much respected form teacher and in English and drama," head teacher Yvonne Brennan told the BBC.