Paramedics and an air ambulance raced to the scene of an emergency - only to find a mannequin left in a parked car.
Crews from the East of England Ambulance Service were alerted at 7.40am on Tuesday to reports of a person unconscious and not breathing in a locked car.
The vehicle was covered in snow and ice, leading to concerns the occupant may have been suffering from exposure to the cold.
But when they arrived at Milton Road in Harwich, Essex, paramedics quickly realised the mistake.
Ambulance service spokesman Gary Sanderson said: "Following assessments at the scene, it appears the person in the car was actually a mannequin.
"This is a very unusual incident our crews attended this morning and the person who dialled 999 did the right thing as they could not gain access to the car and thought the person was not breathing."
The crews were quickly stood down.
Mr Sanderson added the mannequin had been found in "bizarre" circumstances.
It was sitting upright in the rear seat, fully dressed and with a blanket wrapped around it.