A food scandal involving chicken feet has led to public concern in China after it emerged products had been stored in a freezer for nearly half a century.

Police in Nanning, capital of south China's Guangxi Zhuang Autonomous Region, on Friday said they had confiscated more than 20 tonnes of low-quality long-expired chicken feet from a frozen meat warehouse.

Chicken feet, or fengzhao in Chinese, are a popular delicacy. They are often served as a cold dish eaten with a beer.

The chicken feet, some of which were 46-years-old, have caused anger among Internet users.

One post about the feet has been forwarded more than 6,000 times on Sina Weibo, the Chinese equivalent of Twitter.

Some netizens coined a new term "Jiangshi Fengzhao," or zombie chicken feet, to vent their outrage, while others said sarcastically that they might "have a flavor of history."

Most of the chicken feet were illegally imported from foreign countries via Guangxi's border cities like Fangchenggang, said Li Jianmin, deputy director of the public security detachment with Fangchenggang's public security bureau.

"Some illegal businessmen will import uninspected frozen food like chicken feet and have them processed in local food processing workshops or small-sized plants before selling them to vendors across China," Li explained.

Li said the smuggled products contain lots of bacteria and blood, and importers usually soak them in hydrogen peroxide, a banned food addictive in the country, to make the chicken feet look healthy and bright to extend their shelf life.

Li said those involved in the latest scandal will be severely punished.

Staff at Guangxi Entry-Exit Inspection and Quarantine Bureau told Xinhua that diseases can be transmitted in uninspected frozen food, including the H7N9 strain, given that bacteria can live in low temperatures for a long period of time.

Li added that the sewage discharged from these workshops or plants also seriously pollutes the environment.

Fangchenggang police have busted seven cases regarding illegally imported chicken feet since July 2012, with the total value exceeding 20 million yuan (3.3 million U.S. dollars), according to official statistics.

Huge profits are the main reason behind the rampant underground business, Li said, adding that a tonne of chicken feet could guarantee almost 15,000 yuan in profit.

Police in Fangchenggang and other border cities in Guangxi have tightened controls over the imported goods and increased inspection and quarantine to avoid illegal frozen food from entering China.

Any illegally imported food will be destroyed or returned to the exporter in accordance with the law, Li said.

Liu Xiaoling, a professor at the Light Industry and Food Engineering Department at Guangxi University, said the scandal is yet another indicator of the questionable food quality in the country, and the government should have stricter measures in place to avoid possible public health problems.

"China has formulated laws and regulations in the food industry, but they are yet to be improved," she said.

Liu said government bodies should publicize more information regarding food safety to boost awareness of problems that exist.

"The media should also keep a close eye on the government as well as on the food industry to improve China's food safety," Liu said.