(Beijing) - China Food and Drug Administration (China FDA) says it has found 35 restaurants nationwide, including a popular crayfish chain in Beijing, have been using banned chemical additives extracted from poppy shells as seasoning.

The administration has referred 25 cases to local prosecutors' offices for criminal further investigation and they have pressed charges against owners of five restaurants for producing and selling poisonous and harmful foodstuff, China FDA said in a statement on January 20. The regulator said that it is investigating 10 other companies.

The ood safety regulator has banned the use of powdered poppy seedpods, because if food laced with it is ingested over a long-period, it may lead to addiction.

Two food shops in Suzhou in the eastern province of Anhui, with links to food giant Hubei Zhouheiya Co., Ltd, that is known for its cooked and marinated duck meat products are among the companies that have been charged. Hubei Zhouheiya Co., Ltd was not available for comment. Prosecutors have not revealed the trial dates, but the maximum punishment for the charges is a death sentence under Chinese law.

The companies that have come under the direct scrutiny of the China FDA include Beijing Huda Restaurant, a popular crayfish restaurant, with outlets across the capital. But the restaurants manager said he was not aware of any inspections by the regulator.

The China FDA said that the violations linked to poppy shell abuse were uncovered during a field inspection last year, but it did not say how many restaurants or food shops it has inspected.

Seasoning that use extracts from poppy shells are widely used in restaurants serving barbecued fish and hotpot, the inspection found.

The use of poppy shells is part of the traditional cooking style in some areas because people believe it can improve the flavor, Dr. Zhong Kai, a food safety expert in Beijing, said. But Zhong said restaurants and food shops use poppy shell to keep dinners coming back for more.

A nationwide crackdown on the illicit practice might prove to be difficult as the raw materials and seasonings are widely available, he said. There are three to four million, mostly small restaurants and food shops around the country that would make it even harder to stop this practice, he said.

China has been rattled by several food scares resulting from the use of substandard ingredients and abuse of banned additives over the past decade. A scandal involving melamine-tainted baby formula in 2008 prompted authorities to tighten food safety laws.

(Rewritten by Li Rongde)