BEIJING -- A university student from east China's Jiangsu Province has been arrested for attempting to poison three of his classmates.

A student, who declined to be named, was admitted to hospital in north China's Hebei Province on June 8 after returning home due to illness. By that time he was barely able to walk on his own and was suffering severe stomach cramps, vomiting and chest pain.

He recalled that two of his friends also suffered from the same symptoms after a classmate surnamed Chang invited them to supper at the canteen of the China University of Mining and Technology, based in Xuzhou of Jiangsu, on May 31.

The three students were later confirmed to have been poisoned by thallium, according to tests carried out by the China Disease Control and Prevention Center on June 10.

Police in Xuzhou ruled out the possibility that the food in the canteen was contaminated and believed somebody must have poisoned the victims' supper. They tracked down Chang who confessed to deliberately poisoning his classmates.

Chang, a first-year student from the material science engineering department, said the four students used to be close friends but he had been excluded from the group.

According to his confession, he decided to let them "taste the torture of being poisoned," said police. Chang said he diluted the thallium in a bottle of water. At the supper he put the contaminated water in the three students' food when they were away from the table.

Chang's classmates said he was a sensitive loner and that he often felt maltreated by his classmates.

The three victims are still being treated in Chaoyang Hospital in Beijing and are in stable condition.

The case is still under police investigation.