Four pupils were poisoned to death in southwest China's Yunnan province on Monday morning, local government reported.

The four, three girls and a boy, were from Lehong township, Ludian county of Zhaotong city. They developed symptoms of poisoning and died after arriving at school between 8:30 to 9 a.m., according to Ma Jilin, Party Secretary of Ludian county.

One died in the classroom, one on the way to a clinic in Lehong township, where the other two also died. The oldest of the four is about 11 and the youngest only about seven.

The school is attended by more than 500 students. The other students have shown no signs of poisoning.

Ma said the students could have eaten some poisoned food on the way to school, although the reason behind the poisoning is still under investigation.

(Xinhua News Agency, December 4, 2007)