Fears that a couple involved in a crash in which one man died may have lain in a car for three days before being discovered have sparked an independent investigation.
Officers searching for a missing couple confirmed that a man has died and a woman is in a critical condition in hospital following a motorway car crash.
The Police Investigations and Review Commissioner (PIRC) is to carry out an independent probe amid fears the pair lay injured in the car for several days, despite police having been alerted to reports of a crash on Sunday.
Police Scotland said it was called to the southbound M9 near junction nine shortly before 10am yesterday following a report that a Renault Clio had come off the road.
The male driver of the car was pronounced dead at the scene, while the female passenger was taken to hospital in Glasgow.
Police said they believe the incident is ''connected to the ongoing missing persons search'' for 28-year-old John Yuill and 25-year-old Lamara Bell.
The couple were last seen in the company of friends on the south shore of Loch Earn, Stirlingshire, in the early hours of Sunday.
But it has emerged that a call was made to police late on Sunday morning about a car which was reported as being off the road.
Officers said that report was not followed up at the time - something which is now being investigated.
Police were called late on Sunday
The matter has been referred to the PIRC by the Crown Office.
Assistant Chief Constable Kate Thomson, of Local Policing East, said police attended the scene yesterday morning, where the man was pronounced dead while the woman was taken to hospital in Glasgow in a critical condition.
She added: ''We believe that this is connected to the ongoing missing persons search for John Yuill and Lamara Bell.
''It has come to light that a call was made to police late on Sunday morning regarding a car which was reported as being off the road. For reasons currently being investigated, that report was not followed up at the time.
''Officers have notified the families of this update. Our thoughts are with both families at this difficult time.
''A full investigation is currently under way to establish the full circumstances of the incident.''
A spokesman for the PIRC said: "The Crown Office and Procurator Fiscal Service has directed the Police Investigations and Review Commissioner to carry out an independent investigation into the circumstances surrounding the death of a 28-year-old man and serious injury of a 25-year-old woman following an incident at the M9 southbound near junction nine at Bannockburn on July 8."