Forensic doctors and police have found that four pupils in southwest China's Yunnan Province died Monday morning from a kind of highly toxic rat poison, sources with the provincial public security department said Saturday.

The four students, three girls and a boy, were from Lehong Township of Ludian County. They developed symptoms of poisoning and died after arriving at school between 8:30 to 9 AM Monday, according to Ma Jilin, Communist Party chief of Ludian County.

Autopsy report said the four had eaten dry instant noodles and crackling which could have been put in the wrapping bags of the rat poison, which led to their death.

The police have investigated local stores, households, and clinics and found no other cases of poisoning. They ruled out the possibility of malicious poisoning after investigating people relevant to the victims.

However, the rodenticides, namely "Dushuqiang" in Chinese, is widely used in China's countryside to get rid of rats.

(Xinhua News Agency December 8, 2007)