Huang, who came from a poor family in Sichuan, enrolled at Fudan University in 2010 and studied otolaryngology — medicine or surgery involving the ear, nose and throat.

His parents traveled to be at his bedside after hearing he was seriously ill.

"He was good-natured and always helpful," his father said on Tuesday. "He was very popular with his friends. We just can't accept what has happened."

His father earlier told Shanghai TV, "My son was finishing his study through a work-study program. During his eight years at Fudan University, he got the highest scholarship each year."

Huang's high school classmate, Zhou Xu, who works in Shanghai, said:"When we heard he was sick, we just couldn't believe he'd been poisoned."

She said his friend had planned to return home after graduating to be closer to his family.

At the university's School of Medicine, many students had not heard of the incident until Tuesday morning.

"I was shocked," said one PhD candidate of the poisoning allegations. "I can't imagine what might make anyone do such a terrible thing."

Another student living in the same dormitory building as Huang and Lin said, "Lin gets along well with all of us."

Students, with help from Zhou, have begun a collection to raise money for Huang's family.

The tragedy has evoked memories of an incident at Beijing's Tsinghua University in 1994 in which Zhu Ling, a student majoring in chemistry, was left partially disabled after being poisoned with thallium, a substance historically used in rat poison and insecticide.