BEIJING, June 26 (Xinhuanet) -- China's major customs began on Sunday using dogs to help detect smuggling drugs to mark the UN-sponsored International Anti-Drug Day, an official from the China General Administration of Customs said.

These include Beijing, Guangzhou, Shenzhen and Gongbei in Zhuhai, he said.

People passing through the customs would not be horrified when the dogs are sniffing around as the dogs, especially trained for detecting drugs, are small in size and very quiet. They would sit there when they found something suspect, the official added.

Since 1991, when China first began using dogs in its anti-drug campaign, a total of 330 kilograms of smuggled drugs, including 160 kg of heroin and 90 kg of opium, have been found by the dogs.

So far, there are three dog-training centers in China, one in Beijing, one in Ruili in southwest China's Yunnan Province and another in Yantian in Shenzhen. Currently, 40 dogs, mainly German shepherd and Belgium shepherd dogs, are working for this purpose.