A Department of Corrections sniffer dog surprised staff during a training exercise - unearthing "a substantial amount of drug paraphernalia, residual methamphetamine and ammunition".
The dog was being run through its paces at a Hamilton car auction yard when it made the discovery.
Corrections Service support manager Scott Carse said the vehicles, seized by the courts or recovered in accidents, are ideal because they are full of things encountered at prison checkpoints like food wrappers and empty bottles, that act as natural distracters for the dogs.
"However, during the exercise all the dogs indicated on a vehicle that hadn't been set up for the training exercise," Mr Carse said.
"This led to a search by the handlers and what was discovered was a substantial amount of drug paraphernalia, residual methamphetamine and ammunition.
"The staff at the auction yard were as surprised as we were and contacted police.
"The auction yard has welcomed us in to train our dogs for the last three years and it has certainly helped us to develop our dogs into highly trained vehicle searchers working to keep illegal drugs out of our prisons.
"We are very glad we could help the yard by sniffing out these unwanted extras in one of their cars."