India's atomic energy body has given Delhi University two weeks to explain how radioactive waste, which killed a man this week, was sold as scrap.
The Atomic Energy Regulatory Board (AERB) ordered the university to stop experiments using radioactivity.
A scrap metal worker died on Monday after dismantling an irradiation machine sold by the university.
Meanwhile, a university chemist told the BBC that radioactive waste had been dumped in the campus 20 years ago.Professor Ramesh Chandra said "more than 20kg...was buried in front of the physics department during 1986-87." He said that his protests at the time were ignored.
A senior official from the Atomic Energy Regulatory Board said its scientists will be checking Professor Chandra's claim - and would decide on whether the campus should be checked for radiation.