Northamptonshire police have lost a box of bullets after it was left on the roof of one of their cars as they responded to an emergency call.
The Force has referred the incident to the Independent Police Complaints Commission after the box fell on to a road as the firearms officers responded to an emergency in the early hours of Monday.
The box has been recovered but five bullets are still unaccounted for, a force spokesperson said.
Officers with dogs have been conducting searches around the A43 roundabout south of the M1 junction 15a for the missing bullets.
The police have asked the public not to touch anything they suspect to be a bullet and to call 101 right away.