Five cloned dogs, all named Toppy, play at Defector Dog Training Centre in Incheon, South Korea.
Seven cloned Labrador retrievers were unveiled by South Korea's Customs Service on Thursday for use in sniffing out drugs and explosives.
They were born five to six months ago after being separately cloned from a skilled drug-sniffing canine in active service.
The dogs are being trained near Incheon International Airport, west of Seoul.
Using clones could help reduce costs and help ensure a supply of dogs capable of doing critical jobs, officials said.
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 seven new cloned male dogs are all healthy, though one was sent to a university laboratory a few days ago for a minor foot injury it received during training, according to training center head Lim Jae-ryoung.
The team is led by Professor Lee Byeong-chun, who was a key aide to disgraced scientist Hwang Woo-suk. Hwang's purported breakthroughs in stem cell research were revealed as false, but independent tests proved the team's dog cloning was genuine.
7 dogs share the same name
For now, the dogs all share the same name: Toppy, which is a combination of the English words tomorrow and puppy.
"They have a superior nature. They are active and excel in accepting the training," said Kim Nak-seung, a trainer at the customs-affiliated dog training centre.
In February, all seven dogs passed a behaviour test aimed at finding whether they are qualified to work as sniffing dogs.
Only 10 per cent to 15 per cent of naturally born dogs typically pass the test.
If the cloned dogs succeed in other tests for physical strength, concentration and sniffing ability, they will be put to work by July next year at airports and harbours across South Korea, according to the training centre.
Lee of Seoul National University said it cost approximately $100,000 to $150,000 US to clone each of the seven golden Labrador retrievers.