KUNMING - A pupil has died in a food poisoning incident at a rural primary school in Yunnan province, which was caused by highly toxic rat poison known as "Dushuqiang," local authorities announced Wednesday.

Altogether 22 pupils, ranging from first to sixth graders at Xiaoliuzhai Primary School in Hongdian township of Wenshan city, have fallen ill after eating at their school canteen Monday.

They experienced dizziness, nausea and vomiting around 11:40 am after eating rice noodles for lunch and were sent to a local hospital.

"As of Wednesday evening, one pupil had died. Five others are in serious condition, and the other 16 are in stable condition," the Wenshan munipal government said in a statement.

Xiaoliuzhai Primary School is a semi-boarding school with 150 pupils. Seventy-one pupils ate lunch at the school on Monday. Local authorities had also sent the other 49 pupils to the hospital in Wenshan city for medical observation.

"The 49 pupils have not shown symtoms of food poisoning so far, " according to the statement.

Health workers from the Wenshan Municipal Disease Control and Prevention Center had taken food samples for analysis and concluded that the food poisoning was caused by rat poison "Dushuqiang," it said.

Police are investigating the incident.