A postgraduate medical student in Shanghai who police believe was poisoned by a roommate has died.

Huang Yang was pronounced dead at 3:23 pm on Tuesday due to multiple organ failure, Fudan University said on its micro blog.

The 28-year-old fell ill on April 1 after drinking from a water cooler in his room at the college dormitory. Doctors later said he showed symptoms of liver failure.

Suspecting foul play, police tested the water and found a toxic compound. Authorities did not elaborate, but media reports say the substance was N-Nitrosodimethylamine, which can cause liver damage.

Huang's roommate, identified only as Lin, has been detained on suspicion of contaminating the water supply. Investigations are continuing, police said.

However, Fang Ming, a spokesman for the university, denied speculation online and among students on Tuesday that the victim had been poisoned due to jealousy over his good performance in a recent PhD admission test.

On a bulletin board in a building opposite the victim's dormitory, someone had posted a note under a notice about the incident quoting a well-known poem: "We grow from the same root. Why are you so impatient in wanting to boil me?"

The ancient verse is often used to mock people who try to attack a once-close friend.

Fang insisted there was no academic competition between Huang and Lin. They did not have the same major and worked as interns at different hospitals, he said.

The spokesman said the police are continuing their investigation.