A married man who had an affair with Suzanne Pilley is being interviewed by police, after his car was seized as part of the ongoing investigation into her suspected murder.
STV News understands that David Gilroy went with officers voluntarily on Friday morning. Detectives had previously searched his family home in Silverknowes and had already spoken to him as part of the investigation.
Mr Gilroy and Ms Pilley worked together at Infrastructure Managers in Edinburgh and embarked on a relationship. Mr Gilroy is then believed to have left his family home and moved in with Suzanne at her flat in the city's Stevenson area. However, the couple later split and Mr Gilroy moved back in with his family, while Ms Pilley is believed to have embarked on a new relationship.
The investigation into Suzanne Pilley's disappearance moved to the west coast of Scotland on Thursday.
Officers questioned motorists in Argyll and Bute after they launched an appeal for information about a silver family car seen at the Rest and Be Thankful the day after Suzanne's disappearance. Police believe Suzanne was killed and her body left somewhere near an unclassified road between Tyndrum and the Argyll Forest, a 400 mile square area of the region.
Police say they had a "good response" after they appealed to drivers who were in the area on Wednesday May 5 to come forward if they had seen a silver saloon car parked beside a single track or forestry road. They said the car was being driven by a lone-male, and could "hold the key" to the investigation.
Suzanne vanished after making her way to her office in Edinburgh's city centre on May 4.
On Wednesday, detectives said they had uncovered a CCTV image of Suzanne on Thistle Street at 8.55am, just outside her work. The discovery prompted officers to describe the case as a murder investigation, and STV News understands police are working on the theory that Suzanne was murdered in the basement of her office building, before being removed from the scene.
Officers had previously examined footage of Suzanne on a bus, visiting Sainsbury's on Rose Street and walking along North St David's Street. They say the sightings are proof she was making her usual journey to work and had no intention of disappearing.
Suzanne's parents Robert and Sylvia praised the police response and said they believed something "sinister" had happened to their daughter. The couple added: "Suzanne would never put us through this kind of worry intentionally, so we can't help but think she has come to some harm.
"Words can't describe just how devastated we are at this time, each day we are overwhelmed by worry."
The bookkeeper had made her normal trip to work on the Tuesday, taking two buses from her home in the Stevenson area of Edinburgh before arriving outside Infrastructure Managers on Thistle Street. She never showed up at her desk.
A painstaking police probe was launched, with specially trained CCTV analysts and the National Policing Improvement Agency called in to provide assistance, expert support and access to high-tech equipment.
On Tuesday, staff at Suzanne's work joined the appeal and on Wednesday, a spokesman appointed by her firm said: "We were informed by Lothian & Borders Police that they were now treating Suzanne's disappearance as a murder investigation.
"This is clearly a very distressing development for all her friends and work colleagues within the firm.
"We'll continue to co-operate fully with the police in every way possible and hope that anyone with any further information about Suzanne's disappearance will come forward.
"This is an extremely stressful time for her family and her many friends. We are very grateful for the support we've received from the police and others."
Suzanne is described as white, five foot four inches tall and slim, with short, bobbed, light brown hair. She was wearing a light blue waterproof jacket, a red fleece, light blue trousers or jeans and trainers. She was also carrying a shoulder bag and a large water bottle.
Anyone with any information about Suzanne's disappearance or about the silver car's movements in Argyll is asked to contact Lothian and Borders Police on 0131 311 3131 or Crimestoppers on 0800 555 111.