Pigs in southwest China from Friday began having two identity chips fixed on their back legs detailing where they were butchered, examined and sold.

Forty-five markets in downtown Chengdu, capital of Sichuan Province, have started to sell pork with ID chips, said a spokesman with the city's food and drug administration on Friday.

Two plastic rings containing the chips with information on where the pig was bred are fixed around the pig's hinder limbs before it is sold to a slaughterhouse.

Additional information is added to the chips as the pig gets slaughtered, inspected and sold to the end market.

The chip is scanned when each piece of pork is sold so that the customer can have a receipt with a code that links to an entry that records the slaughter, inspection and sale of the pork in a city database.

Every seller is required to scan the chip of meat they purchase so that the system logs how much pork they have in stock. Meanwhile, their electronic scales are linked to the market system to keep track of how much pork they sell.

"The amount of pork sold must not exceed that of pork purchased. That way we make sure no pork comes from illegal channels," the spokesman said.

The customer could inquire about the pork by phone, text message or on the administration's website to ensure it was safely bred, butchered, stored and transported as well as properly examined.

Pork seller Wu Bo welcomed the policy. "Customers can now buy without hesitation. With the chips, they can eat without worry," Wu said. "If anything goes wrong with the quality, we know who to blame."

The city government and seller pays for every identity chip, which costs two yuan (29 U.S. cents), the spokesman said. "The cost is too small to affect the pork price."

The chips were tightly fixed and were almost impossible to take off without breaking them, the spokesman said in response to questions on whether the identity chips can be swapped.

Each of the pork pigs sold in Chengdu will get ID chips by the end of next April, the spokesman added.