A drugs dog sent into East Oxford pubs and clubs has sniffed out more than 30 drug users and dealers.
And officers believe the dog - a privately trained black labrador - has identified a "significant" Class A drugs dealer.
The 21-year-old woman, from Witney, who has not been named, was spotted by the sniffer dog outside Tesco, in Cowley Road, during an operation on February 1.
The woman was arrested and is due to answer bail next month.
Sgt Andy Barefield said: "The drugs dog nearly hauled the handler's arm off when he walked past her."
Drugs, believed to be cocaine, ketamine and ecstasy, were seized.
Following an operation on January 18 in which the dog sniffed out a suspect, officers searched a house in Cosin Close, off Manzil Way, Oxford. They found computer equipment believed to have been stolen in a recent burglary, drug paraphernalia, and paperwork relating to false identification.
A man from Abingdon was arrested after an operation on February 6 in which suspected Class C drugs were seized.
The operations, which were run in partnership with Nightsafe, have been running regularly since September.
Since December, 70 people have been searched after being sniffed out by the dog.
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