A lorry driver from the West Midlands strangled his nine-year-old stepdaughter in the back of his cab before hanging himself.

The 40-year-old man took the Spar delivery lorry from his employer, Willenhall-based AF Blakemore & Son, on Friday. The girl’s body was discovered in the cab of the lorry, which had been parked in a lay-by near a Little Chef on the A605 near Warmington, Northamptonshire, the following day.

The man was found hanging from a tree in nearby woodland.

Police are trying to establish whether there had been a sexual motive for the attack and were due to name the dead girl, after discussions with her family.

The stepfather, who told the girl he was taking her for a “special treat”, is believed to have taken the lorry from AF Blakemore & Sons, in Rose Hill, in the early hours of Friday.

The alarm was raised by staff after it failed to return to the base in Long Acres Industrial Estate by Saturday afternoon. Worried bosses called the police and the lorry was found, unlocked and with its cab curtains drawn, thanks to an onboard tracking device.

Blakemore spokeswoman Charlotte Ashby said: “We are deeply saddened. We will of course be offering the police our full support. In the meantime our thoughts are with the families of those affected.”

Detective Chief Inspector Tricia Kirk, believed the man and the girl’s mother had been together for a year. DCI Kirk said the mother had no concerns about her daughter’s safety before the tragedy unfolded.

She said: “I cannot begin to imagine what the family are going through and we have family liaison officers with them trying to answer any questions that they may have.

“At the moment, we are treating it as a murder suicide. We believe the little girl was murdered and the man then committed suicide.”

Police said the pair began their journey about 3am and were seen in Peterborough later that afternoon. They were called to the rural lorry park at about 2pm on Saturday.

They tried to resuscitate the girl but were unable to do so and after searching the area, found the stepfather hanging from a tree nearby.

DCI Kirk added: “The man is part of the family set-up and they have a close relationship as stepfather and child.

“The mother was comfortable with the child being with the male, and there were no issues or concerns raised within the family.

“Our investigation is to try and find out what led to this tragic event taking place.”

Northamptonshire Police will be revealing the identities later today.