Two men died after their car was in a crash with an ambulance in the early hours of Sunday morning.
The accident happened at about 6.11am in Peterstow, close to Ross-on-Wye, Herefordshire.
The ambulance was not responding to a 999 call before the crash, and two of its staff were also hurt, but their injuries are not thought to be serious.
Sergeant Dan Poucher, from West Mercia Police, said an inquiry was under way and urged witnesses or people with dashcam footage to contact police.
"Next of kin have been informed and our thoughts are with the families of those affected," he said.
The car driver and passenger were both pronounced dead at the scene, on the A49 outside Pengethley Garden Centre.
A West Midlands Ambulance Service spokeswoman said four ambulances, three paramedic officers and an emergency doctor from Mercia Accident Rescue Service responded to the crash.
"The trust will work closely with officers from West Mercia Police on the investigation which is already under way," she said.
Witnesses should contact the force on 101, quoting reference 155s 250819.
