Cloned dogs are helping sniff out issues at outh Korea's airport customs.

Six genetic duplicates of a single Labrador retriever have been working at the country's main Incheon international airport and three other customs checkpoints to deter drug smuggling. First they had to go through 16 months of training.

They are part of a litter of seven born in 200, cloned from a skilled drug-sniffing dog. They were all named "Toppy" — a combination of the words "tomorrow" and "puppy." One was injured in training and dropped out.

(For more on cloned puppies, click here.)

The cloning work was conducted by a team of Seoul National University scientists who in 2005 successfully created the world's first known dog clone, an Afghan hound named Snuppy.

The agency has said clones could help reduce costs inherant in finding dogs who can handle the critical task of sniffing out contraband. Only about three out every 10 naturally born dogs it trains end up qualifying for the job.