A second woman is being questioned over the murder of a 60-year-old businesswoman.
Detectives investigating a knife attack on Sadie Hartley at her home in Helmshore, Lancashire, said a 55-year-old woman was arrested at an address in Chester on Monday afternoon on suspicion of murder.
A 34-year-old woman from Chester who was arrested on Sunday in connection with the death is continuing to be questioned in custody.
The mother of three, who ran a medical communications business, was found stabbed to death in the hallway of her house on Sunny Bank Road in the village on Friday evening.
She was alone at the time as her partner Ian Johnston, an ex-fireman, was abroad on a skiing holiday in the Swiss Alps. Police have said he is not a suspect.
Nothing was believed to be missing from Ms Hartley's home, a large detached, stone-built property, and there was no forced entry.
Ms Hartley suffered defence injuries as she fought back from the attack, launched possibly on her doorstep.
Detectives said Ms Hartley died in a "targeted attack" but said the motive remains unclear.
The murder weapon has not yet been recovered as searches continue.
Detective Superintendent Paul Withers, leading the investigation, said: "I'd like to thank everyone, particularly the residents of Sunny Bank Road, for their help and patience with the investigation so far.
"The exact motive for this horrific murder remains unclear at this time but we are continuing to make steady progress and I would urge people to help us with our further lines of inquiry today."
A director of her own business, Hartley Taylor, based in Knutsford, Cheshire, the victim was last seen alive on Thursday at a conference in Manchester with a colleague.
She was last in contact with a friend and work colleague at around 7.30pm on Thursday evening, then stopped answering emails, which was unusual.
Police believe she was murdered sometime on Thursday evening.
Officers are continuing their appeal to identify a person seen passing a man as he walked out of Sunny Bank Road on Thursday evening and an unknown person who walked into the cul-de-sac, leaving a few minutes later.
They also want to trace the driver of an old style Renault Clio car which was seen arriving in Sunny Bank Road just before 8pm on the same night, and drove off moments later.
Mr Withers added the investigating team was also keen to hear from anyone who may have information about people asking for the location of Sunny Bank Road in the days or weeks leading up to the murder.
Anyone with information should call 101 quoting incident reference 1481 of January 15, or alternatively contact Crimestoppers anonymously on 0800 555 111 or online at Crimestoppers-uk.org.