Six cloned Labrador retrievers are now using their olfactory prowess to help officials find drugs and explosives at airports and harbors across South Korea. The dogs—which all share the name “Toppy,” a combination of “tomorrow” and “puppy”—became the world’s first working cloned sniffer dogs when they reported for duty last Thursday, according to BBC News.

Thanks to a highly successful drug-detecting donor dog from Canada and 16 months of training, the new class of recruits, customs officials hope, will increase performance and decrease costs.

"They have a superior nature. They are active and excel in accepting the training," Kim Nak-seung, a trainer at the Customs Service-affiliated dog training center told MSNBC in April.

Fewer than 10 percent of naturally born dogs are typically qualified to become professional sniffers, based on a behavior test and rigorous physical training. All seven dogs in the cloned litter passed the test, and only one puppy didn't complete the training—due to an injury.

Scientists from Seoul National University helped clone the Toppys, as well as the world’s first cloned canine in 2005, an Afghan Hound named Snuppy. (That institution was also home to the work of Woo Suk Hwang, who fabricated spectacular results on human embryonic stem cells; Snuppy turned out to be a genuine success.)

But dog duplication extends beyond South Korea. Last month marked the arrival of five cloned German Shepherd puppies from a 9/11 hero named Trakr. “His many remarkable capabilities were proven beyond all doubt on our nation's darkest hour—and we view the work of cloning him as a great honor,” Lou Hawthorne, CEO of BioArts International, told The New York Daily News. Trakr helped locate the last human survivor at Ground Zero, according to BioArts, which held a contest to pick a clone-worthy dog last year and subsequently did the cloning.

"If the clone has Trakr's abilities, then of course we'll put him into service as a detection dog," James Symington, the deceased Trakr’s former master, told the Daily News after learning that part of his dog would "live on."

Animal rights groups, including the Humane Society and the American Society for the Prevention of Cruelty to Animals (ASPCA), caution against the cloning of companion animals. They note potential physiological problems that can result from cloning, as well as the pet overpopulation problem.

But what if the genetic duplicates are working to keep people safe? Would they still be opposed?

“We are against the cloning process regardless of the use,” responds Kathleen Conlee, director of program management for animal research issues at the Humane Society. “No cloned dog or cat has lived long enough to know all the long-term ramifications.”

Photo of Toppys and trainer by Lee Jin-man / AP