A small amount of radioactive, weapons-grade plutonium has gone missing from a university in Idaho, The Independent reported.

Idaho State University was using the radioactive chemical element, which was about the size of a 10p piece, for research.

The US Nuclear Regulatory Commission said the university could not account for about a 30th of an ounce (one gram) of the material, which is used in nuclear reactors and to make nuclear bombs.

While the amount is too small to make a nuclear bomb, it could be used to make a dirty bomb to spread radioactive contamination, said Victor Dricks, a spokesman for the agency.

“The NRC has very rigorous controls for the use and storage of radioactive materials as evidenced by this enforcement action,” he said of the proposed fine of $8,500 (£6,280) for failing to keep track of the material.