It took 300 million Korean Won (£150,000) of state funding, but the cloning has been successful.

"The project was successful," said Lim Jae-Yong, the project manager for the team working on the cloning effort.

"This is the first time that cloned dogs have been used as sniffer dogs."

Seven cloned embryos were created using cells taken from a Canadian Labrador Retriever called Chase and successfully implanted into three surrogate mothers.

Customs officials have decided to call the puppies 'Toppies', a contraction of 'tomorrow's puppies.'

The Toppies have evidently inherited Chase's talents -- they passed the first round of tests for behavioural patterns and genetic qualities.

"They will report for duty in June after completing a second round of training," said Lee Ho, spokesperson for South Korea's customs service.

The cloning project came about when the customs service decided that it would be easier to clone the best sniffer dogs as opposed to training them from scratch.

For lead geneticist Lee Byeong-Chun, the breakthrough is another first -- he played a key role in the first ever successful cloning of a dog, a three-year-old Afghan Hound.