Police investigating the Renee MacRae mystery are conducting new tests on blood found in the boot of the mother-of-two's burned-out car 28 years ago.
Police have begun excavating the quarry near the lay-by
The investigation team has just begun excavating Dalmagarry quarry near Inverness in the hope of discovering whether the 36-year-old's body was dumped there along with her three-year-old son Andrew.
Detective Superintendent Gordon Urquhart said that Northern Constabulary was also revisiting other historical evidence relating to her disappearance in November 1976.
When Mrs MacRae's BMW was discovered, traces of blood were found in the boot and this has now been sent to Aberdeen for fresh forensic analysis.
Det Supt Urquhart said the investigating team had managed to "clean up and amplify" some of the evidence that was available 28 years ago to an extent that they were beginning to understand the case in more detail.
He said: "I think some of that detail is pretty significant.
"The lab that we work with at Grampian Police laboratory in Aberdeen are still reviewing the evidence that was recovered 28 years ago.
"We gave them that task a couple of weeks ago and they are still working on it and they've got some positive results there even now.
"Sampling the blood for DNA is part of the work they're doing and we're hoping that in the next week or two we'll get more of a result on that."
Renee MacRae had been having an affair with Bill MacDowell, who was her husband Gordon's accountant.
Mr MacDowell, who now lives in London, is the father of Andrew, who vanished along with his mother. Earlier this month, Mr MacDowell told the Sunday Mail newspaper he did not kill his lover and her son.
She had been said to be going to meet him on the night she disappeared but Mr MacDowell said he decided against it.
Renee MacRae's car was found on the A9 in 1976
Mrs MacRae left Inverness at about 1700 GMT on the evening of Friday 12 November and her abandoned car was discovered burning at Dalmagarry, south of Inverness, at about 2200 GMT.
Excavation of the nearby quarry has begun, with forensic archaeologists saying they are initially targeting a number of areas which they believe could be the most likely site of remains.
Professor Sue Black, the forensic anthropologist working on the dig, said the time was right to revisit the case.
She said: "Forensic science has moved on enormously since 1976, there are many things that we can do now that we couldn't do then and we felt that this was a time where if there is anything there we've got a better chance of finding them now than we ever have before."