NANNING -- Amazonian snails, a restaurant delicacy that has made many people ill, are now being blamed for killing crops on more than 160,000 hectares in southwest China's Guangxi Zhuang Autonomous Region.

Farmers near seven cities in Guangxi have reported an invasion of Amazonian snails in their paddy fields. Agricultural experts here said rainy weather, brought by this summer's typhoons, created ideal conditions for the snails. Annoyed by their quick proliferation farmers are using pesticide to kill the snails.

Meanwhile, the Beijing Office of Food Safety issued an urgent notice over the weekend, calling for tighter supervision over aquatic products and safety inspection in supermarkets, shopping malls and restaurants. The office also warned people against eating raw fish, shrimp, snail, crab, frogs and snakes.

The large, black snails were a hot-selling aquatic product in big Chinese cities like Beijing. However, 23 people in Beijing alone have fallen ill after being infected by eel worms found in Amazonian snails, according to the Beijing Health Bureau. The patients suffered from fevers and stiff neck after eating Amazonian snail salad and a spicy snail dish in restaurants.

According to Xu Rongman, researcher with the Institute of Microbiology and Epidemiology under the Academy of Military Medical Sciences, each Amazonian snail is host to 3,000 to 6,000 parasites, which can harm the human nervous system, leading to headaches, facial paralysis, meningitis and fever.

Amazonian snails originated in South America and first came to China in the 1980s. The first patient to fall ill after eating the snails was reported in Guangzhou, capital city of south China's Guangdong Province.