Police Scotland has defended its original search at the scene of last year's fatal M9 crash after being alerted to "debris" at the site last week.

The force said it has been in direct contact with the family of one of the crash victims, Lamara Bell, over the matter and was working to establish whether the items recovered on Friday were linked to last July's collision.

Ms Bell, 25, and John Yuill, 28, died after lying in a crashed car for three days after the incident was first reported to police.

Mother-of-two Ms Bell was critically injured in the crash off the motorway near Stirling and later died in hospital. Mr Yuill, her partner, died at the scene.

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It emerged that a phone call to police reporting a vehicle off the road on July 5 was not followed up.

The Lord Advocate is currently considering the findings of an independent report before deciding if any action, such as a fatal accident inquiry, should follow.

The Scottish Sun on Sunday has reported that Ms Bell's family found car parts at the scene. It followed a family visit to lay flowers to mark one year on from the crash.

Her father Andrew, 50, said he raised the alarm over debris, which he believes is from the car his daughter was in.

He told the newspaper: "I've picked up dozens of bits of plastic in undergrowth at the crash site - including a big chunk which looked like it could be a bumper attachment.

"There were also smaller pieces of plastic the same shade of blue as the Renault Clio."

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He added: "I would have hoped the police would have gone above and beyond to make sure their investigation was done right."

Chief Superintendent Stephen McAllister, the Forth Valley Commander, said: "Police Scotland has been made aware of information relating to debris at the scene of the crash on the M9 last July.

"I would wish to reassure the families and the wider public that following the incident, specialist officers conducted an extensive search of the crash site.

"This resulted in the recovery of the vehicle and items found nearby which were examined during the investigation into the crash.

"We have made direct contact with the Bell family and have recovered the debris to establish its source.

"We have advised the Crown Office and will carry out the necessary investigation to try to establish what link, if any, these items have to the accident.

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"I would again extend my sympathies and those of Police Scotland to the families of Lamara Bell and John Yuill at this difficult time."

It is understood the force was made aware of the debris on Friday and it was recovered on the same day.

A Crown Office spokesman said: "We have been made aware of this matter by the Police Service of Scotland and at this stage it would be inappropriate to comment further."

Scottish Liberal Democrat leader Willie Rennie said: "One year on this turn of events must be agonising for family and friends who have endured the horror of the crash and the aftermath.

"The police need to explain what has happened. If further evidence has been discovered then we do need that explanation urgently."

Two investigations were launched following the crash - one by the police into the actual crash and another by the Police Investigations and Review Commissioner (PIRC), which was tasked with examining the wider circumstances surrounding the deaths.

A PIRC spokesman said: "The commissioner submitted a supplementary report to the Crown Office and Procurator Fiscal Service (COPFS) last month on her independent investigation into the circumstances surrounding the deaths of John Yuill, 28, and Lamara Bell, 25, following the recovery of a car close to the motorway at Bannockburn on 8 July 2015.

"The COPFS is now considering the content of that report, along with the interim report submitted in November last year."