Police probing the disappearance of a mother and toddler more than 40 years ago have found bones and parts of a pushchair after draining a 100ft quarry.

Renee MacRae, 36, and her son Andrew, three, disappeared on November 12, 1976, from their home in Inverness, Scotland.

Her bloodstained BMW was then found burnt out on the A9 around 12 miles south of the town, prompting speculation they were murdered, but their bodies were never located.

Last month officers began draining Leanach Quarry at Culloden, around four miles away, and are now analysing remains they discovered to see if they are linked to Ms MacRae and her son.

Renee MacRae, 36, and her son Andrew, three, pictured, disappeared from Inverness in November 1976 and police have today revealed they have found bones and parts of a pushchair in a quarry officers have been searching as part of the investigation

Police have drained the 100ft Leanach Quarry, pictured, at Culloden, around four miles from Inverness, and are still analysing remains that were found

Ms MacRae, left, was driving to Perth with Andrew, right, to visit her married lover Bill McDowell on the day she disappeared. Her estranged husband Gordon was questioned but has always denied involvement

Ms MacRae was on her way to see her lover and Andrew's father Bill McDowell, pictured last year. He was initially questioned over her disappearance but had an alibi and has always denied any involvement

They pumped out almost 3million gallons of water from the quarry to be able to conduct a proper search.

Ms MacRae, 36, left her home in Inverness with Andrew on November 12, 1976, heading south.

Estranged from her husband, Gordon, she was driving to Perth to meet her married lover, Bill McDowell, who was Mr MacRae's accountant and Andrew's father.

She had previously dropped her older son, also Gordon, then nine, with her estranged husband before setting off for Perth.

Police re-examined the case in 2004 and named a suspect in a report to the procurator fiscal in 2006.

However, the Crown Office said there was insufficient evidence to bring a prosecution.

Mr McDowell, who now lives in Cumbria, was questioned by police but strongly denied having any involvement, a position he has maintained for decades.

Last month a source close to the investigation said the search of the quarry was prompted by new information that came from a public appeal.

The source said Police Scotland believed the searching the quarry was the 'best chance they had of solving the case'.

Leanach Quarry was first searched in 1978. Divers using underwater cameras were said to have caught sight of a head inside a plastic bag.

But the debris they retrieved failed to find any evidence of their remains.

Mr McDowell was already married and had previously worked for Ms MacRae's husband as his accountant. He is pictured here in 1976 with wife Rosemary

Police released this picture of a Silver Cross pushchair identical to the one used by Ms MacRae earlier this month as part of the investigation

Forensic teams have been sifting through car parts and discarded metal, pictures, and have found parts of a pushchair similar to one Andrew had

Speaking today, Detective Inspector Brian Geddes said: 'As part of the search operation at Leanach Quarry numerous items have been found to date, many of which have warranted further research and examination.

'Meticulous analysis is now ongoing to establish if any of these items would be relevant to the investigation into the murders of Renee and Andrew MacRae.'

It is believed that so far forensic teams have only identified animal parts but analysis of the skeletal remains continues.

A source close to the investigation said that the pushchair wheels and metal parts appeared to be very similar to the make of buggy used by Ms MacRae.

A number of cars have also been removed from the quarry.

Scientists are checking material as it is pulled from the bottom of the quarry in huge shovels before lorries transfer the debris to a location off-site.

There, a 16-strong team of specialist officers is carrying out a fingertip search through the mud.

The operation, led by Detective Inspector Geddes, has involved personnel from the fire service and the Scottish Environmental Protection Agency.

A police officer is pictured walking past the quarry in Culloden, from which nearly 3million gallons of water were drained

Detective Inspector Brian Geddes, pictured at the quarry, said 'meticulous' analysis is going on to discover if anything found is linked to the disappearance of Ms MacRae and her son

This month police released a picture of a Silver Cross pushchair identical to the one used by Ms MacRae.

It was believed to have been with the mother and son when they went missing but has never been found.

An initial search of Dalmagarry, another quarry close to where the car was recovered was quickly abandoned, despite reports from an officer that he could smell decomposing flesh.

A dig at Dalmagarry lasting a month and costing £100,000 was carried out after the cold case review in 2004 but no human remains were found.

In November last year Mrs Macrae's sister Morag said she was hoping one day to be able to lay them to rest.

She said: 'Not a day goes past that both are not in my thoughts.

'Even after the passage of time I believe that there are people who know what happened to Renee and Andrew, and I will never give up hope of getting justice for them both.

'I appeal for anyone with any information to come forward and for others to examine their conscience to end 42 years of pain and anguish to allow us to grieve for Renee and Andrew.'