Police have searched the grounds of a stately home in Hertfordshire for a man suspected of murdering his former partner.
The body of 34-year-old Red Cross worker Angela Hoyt was found at her home in Glebeland, Hatfield on Tuesday.
About 30 officers searched the grounds of Hatfield House after reported sightings of Martin Collett, 35.
Police believe he has connections in a number of places including Southampton, Bristol and Stratford-upon-Avon.
They had earlier said Mr Collett could be anywhere in the UK.
Det Ch Insp Mark Ross of the Bedfordshire and Hertfordshire Major Crime Unit thanked members of the public who had given the force information.
He added: "Understandably this is an extremely difficult time for Angela's family and it is vitally important we trace Martin Collett as soon as possible."
Ms Hoyt's family in Canada alerted police following concerns about her which led officers to break into her home.
She is thought to have died between 22 and 24 May.
Ms Hoyt was born in Windsor, Ontario, and moved to the UK in 1999.
She is survived by her parents, Barb and Dwight Hoyt, her identical twin sister Ami Watanabe and Ami's husband Garry, and niece and nephew Tori and Kai.
In a statement released through Hertfordshire Police, Ms Hoyt's family said: "Angela was a very ambitious and driven girl.
"She had a passion for human rights and wanted to use her work to help improve the lives of those less fortunate. She had strong opinions and convictions."
Ms Hoyt had recently returned from a three-month role in Pakistan as part of her work with the International Committee of the Red Cross.
She had been working as a public affairs and communications adviser for the organisation since February 2008.
Her family added: "Her niece and nephew were a great source of pride and she was an awesome aunt to them.
"She always picked up very thoughtful treasures for them on her travels. She was very close to her parents and twin sister.
"Angela had an infectious smile; it lit up the room."
Officers have not released any further details about how Ms Hoyt died.