Four people were killed on Friday after a mid-air collision between a light aircraft and a helicopter in southern England, police said.
The incident took place just after 1200 GMT at Upper Winchendon, near the village of Waddesdon, about 45 miles (72 km) to the northwest of London.
"Officers are in the process of working to locate and support their next of kin. The Air Accidents Investigation Branch has been informed and their staff have been on the scene," Superintendent Rebecca Mears, from Thames Valley Police, said in a statement.
Police said officers and members of other emergency services including the fire and ambulance services attended the scene.