French police have reportedly arrested a couple 31 years after their daughter was found dead, in a cold case revived through DNA evidence.

The mutilated body of the girl, who was unidentified, was found by the side of a motorway in central France in 1987.

The parents were traced after the DNA of their son, tested in an unrelated case, was matched with that of the girl, French media report.

They are to be questioned by a judge on Thursday and could face murder charges.

The parents have not been identified but are believed to be in their sixties. Police have not commented on reports of the arrests on Tuesday.

'Little martyr'
The body was found in a ditch along the A10 motorway near the city of Blois in August 1987. The authorities were unable to identify her and she was believed to be between three and five years old at the time of her death.

The girl bore marks of horrific, long-standing abuse, such as broken bones and burns with an iron. Parts of her body were mutilated.

She was nicknamed the "little martyr of the A10", and buried in an anonymous grave.

The case baffled police for decades. It was reopened in 2012 when a call for witnesses was released with a picture of the dead girl's face and the caption: "Who is she?"

The girl was described as having a blue checked shirt, curly black hair and a "Mediterranean (maybe North African) type".

The apparent breakthrough happened last year, when a man was arrested over a violent incident.

His DNA reportedly identified him as the victim's brother. Months of investigation then led police to the parents.