A woman passenger passed away in a van before she could reach doctors at Northampton General Hospital, according to police.
Eyewitnesses said several police cars were called to Cliftonville car park at NGH at around 1.30pm yesterday.
Officers taped off a Ford Transit van and a blanket had been placed across the vehicle's windscreen.
However a police spokesman said the force was called "purely to investigate a non-suspicious incident in the car park."
A woman was found to have passed away within the Transit van and was declared deceased by hospital staff.