Express mail service has unwittingly become an accomplice of drug smugglers, Shanghai Customs said.

So far this year, eight of the nine drug smuggling cases intercepted at Shanghai ports were via parcel post, according to customs. The number was 16 out of the 28 cases last year.

Moreover, people who sign to receive the mail in these cases are usually not the drug dealers, according to the authority, and lawbreakers now tend to use young women as smuggling tools.

In a typical case this year, a man became acquainted with a woman in Shanghai and later asked her to receive a parcel of clothes from overseas as a favor.

It contained more than 700 grams of heroin inside.

After investigation, the authority found that the man used several online chat groups in which he had lists of people helping him collect the parcels from abroad.

In the 2010 Annual Report on Drug Control in China, the narcotics control bureau of the Ministry of Public Security listed express postal service as one of the key parts in the fight against drug smuggling.

Customs officials said people should not innocently collect mail for others to avoid being involved in drug smuggling.

Jiang Wenqing contributed to this story.

Contact the writer at zhouwenting@chinadaily.com.cn