National prosecution authorities will investigate and severely punish duty-related instances related to food-safety crimes, the Supreme People's Procuratorate (SPP) said on Friday.

Food-safety crimes occur frequently and are mainly blamed on weak supervision by relevant authorities as well as dereliction of duty of some law enforcement officials, Zhang Bencai, spokesman for the procuratorate, said at a news conference on Friday.

"We will actively investigate job-related crimes, including supervision malfeasance and accepting bribes involving food-safety crimes and severely punish them according to the law," he said.

Meanwhile, prosecuting authorities at each level will supervise the probes to prevent any illegal behavior, such as using fines rather than criminal punishment or covering the crimes, according to him.

Figures provided by the procuratorate show that in 2013 alone, national prosecution departments investigated 531 people accused of dereliction of duty involving 362 food safety cases.

A typical case occurred in April, when Kunming City People's Intermediate Court upheld the verdict of a lower court that sentenced Sai Yue and Han Chengwu — the former director and deputy director of Songming county administration of quality and technology supervision — in prison for accepting bribes and supervisory malpractice.

In September 2011, Sai and Han investigated a local food-processing company, discovering it didn't have a license and that more than 2,000 metric tons of lard didn't meet safety standards, according to the court.

They decided to seal 591 tons of the lard and fined the company 1.4 million yuan ($230,000).

But in October, Sai and Han reduced the fine to only 200,000 yuan. They also broke the seals, allowing the lard to be sold, which posed a threat to people's life and health, the court said.

According to Songming prosecutors, Sai and Han accepted 130,000 yuan from the company for their help.

In 2012, they were charged with accepting bribes and malpractice for food supervision.

On Friday, the Supreme People's Procuratorate publicized five typical cases involving food-safety crimes to guide prosecuting departments in correctly understanding the standards in arrest and prosecution procedures.

"Crimes related to food safety can seriously harm people's health, undermine economic order and affect social stability," said Chen Guoqing, director of research department under the Supreme People's Procuratorate.

Food safety crimes often occur on the black market, where production is unregulated and factories may be dirty and poorly equipped.

According to Chen, most of the suspects were running small private businesses, which practiced unsafe food­—handling methods.

Huang He, deputy director of the public prosecuting department under the top procuratorate, said such cases often involve organized crime, with members assuming different roles, including manufacturing, selling, transporting and storing products, to form a complete interest chain.

Data released by the procuratorate show that from 2011 to 2013, national prosecuting authorities arrested and prosecuted 6,128 people involving 2,705 cases of producing and selling shoddy food.

Meanwhile, the authorities arrested and accused 10,975 people found in 7,298 criminal cases for selling toxic and harmful food.

Li Wei, lawyer from the Beijing Law Society, said the key to tackling such crimes is to eliminate corruption in regulatory bodies.

Other administrative authorities, such as industry and commerce management and quality supervision sectors, also should tighten supervision, she said.