A motorcyclist in his 60s died after coming off his bike near Southam despite rescue efforts by passersby and ambulance staff.
And police now want help tracking down the driver of a tractor who was nearby and may have vital information to shed light on events.
The rider had suffered multiple injuries when he was found on the Banbury Road between Southam and Ladbroke just before 7pm on Sunday.
He was pronounced dead at the scene after ambulance crews, paramedics, and air ambulance teams provided emergency help.
A number of passersby and motorists also at the scene to try and save the man whose age and name is not yet known.
A West Midlands Ambulance Service spokesman said: “When crews arrived they found a man who had suffered multiple serious injuries. A number of members of the public were at the scene providing support.
“Ambulance staff immediately started assessing and treating the man, but sadly his condition worsened and despite all of the efforts made, it was not possible to save him and he was confirmed dead at the scene.”
Nobody else is thought to have been hurt in the incident.
A Warwickshire Police spokesperson said: “The collision involved a grey Honda motorcycle, just before the turning for Ladbroke.
“Despite the best efforts of the paramedics who attended, the rider of the motorcycle, a man in his 60s, sadly died at the scene.
“His next of kin have been informed.
“Officers investigating are appealing to trace the driver of a blue and white tractor who had been in the area and may have vital information regarding the circumstances leading up to the incident.”
Contact police on 101.