Chinese state media say two girls have died after eating poisoned yogurt placed outside their kindergarten at the direction of the head of a rival school.

The Xinhua News Agency says police believe the poisoning was motivated by competition for students between the schools.

It says the woman confessed that she injected the yogurt with rat poison and asked a man to place it with notebooks on the road to the rival kindergarten in Pingshan county in Hebei province.

Xinhua said Thursday that the girls’ grandmother found the books and yogurt and took them home on April 24. The children suffered convulsions after drinking the yogurt and died later.