Police in Dunedin believe a bag of tear gas cartridges it lost fell off the back of an Armed Offenders Squad vehicle.
Police are appealing to the public for the return of the black bag and its contents, lost last Thursday.
The bag contains a silver canister of tear gas marked CS in blue writing, and five tear gas cartridges about the size of shotgun rounds, and has not been found despite extensive inquiries.
Police say they believe the bag fell from a vehicle between St Andrews St and the Southern motorway during a callout to a domestic incident on Thursday night in Mosgiel.
If found the canister and cartridges should not be tampered with, police say, but handed in or anonymously called in via the Crimestoppers line.
They say they are running an internal investigation into how the bag was lost.