Sniffer dog Sandy has a nose for large sums of money, especially if it comes from a drug deal.

The two-and-a-half year old Labrador is one of a pair of hounds unveiled by Customs and Excise as the latest weapon in combating the trade in illegal drugs. Their eight-months' intensive training cost £15,000.

Sandy and his partner Bodie have been trained to sniff out large sums of cash, whether or not the notes have come into contact with drugs.

They are now working on the beat at London's Gatwick and Heathrow airports where they will hunt for the proceeds of deals hidden in luggage, cargo or on the person.

Trained on sterling

Sandy's handler Paul Farrell, 29, said the dogs regarded the job as a big game of hide and seek:

"We trained them on sterling currency that has been chopped up to playing-card size and hidden in different samples in various places," he said.

"When they find the money they are rewarded. My dog barks and wags his tail and then will start to dig when he smells something. Then he will be rewarded with a toy, bone or shoe to play with."

Sandy and Bodie were officially introduced to the public at a travel show in London by Paymaster General Dawn Primarolo.

Miss Primarolo said the dogs could trace "vast amounts" of money but stressed they would be targeted on people suspected of drug dealing rather than those with legitimate reasons for carrying large amounts of cash.

"The dogs are deployed after intelligence has been received and work without disrupting the honest traveller," she said.

Dogs may smell ink

Sandy and Bodie can be used in up to nine daily searches, normally targeting flights from Latin America and the Caribbean.

Although officials are uncertain how the dogs can detect large denominations of notes, they believe it may be due to the smell of the ink used.

Mr Farrell said: "We train them to find English sterling but they have found different types of money. There seems to be no limit to what the dogs can search for as long as they are rewarded and their interest maintained.

"They can smell through steel containers if there is air coming through."

Since the pilot scheme for using dogs to detect cash was launched in June, the two dogs have found £500,000 between them.

Customs may now train further dogs to track the scent of money.