In a sense they are indispensible: the dogs have helped in the seizure over 600 kilograms of drugs and 5.25 tons of acetic anhydride, a drug precursor, in a decade or so since the Urumqi customs district set up its drug detection dog training base.

A typical day at the training base starts from the early morning, when trainers check and clean up the kennels. The kennels' dwellers then receive regular trainings until noon. At noon, the dogs are taken to places under customs supervision: an international airport, for instance.

After the arrival, they will be assigned different sniffing targets, which include vehicles, luggages and flight passengers. The field tasks usually last from noon to the end of afternoon.

A detection dog is rewarded for each successful task. Like kids, dogs also need incentives to make progress, said He Feng, a local drug control official in charge of the detection dogs.

Labrador drug detection dog Kadi takes part in a luggage sniffing training with its trainer, Lu Hua, in a training base in Urumqi, Northwest China's Xinjiang Uygur autonomous region, June 21, 2012. [Photo/Xinhua]