International Atomic Energy Agency inspectors have discovered that Iran had produced and experimented with Polonium, an element useful in initiating the chain reaction that produces a nuclear explosion.

According to a report the inspectors will submit to the United Nations this week, Iran reportedly acknowledged the experiments but offered an explanation involving polonium's non-weapon uses, including power generation, The Washington Post reports.

The IAEA noted the explanation and left the issue 'hanging there', the daily quoted one person familiar with the matter as saying. The experiments were described by this person as occurring 'some time ago'.               

Iran had opened its facilities for IAEA inspections to show the world it does not have nuclear weapons programme.

Polonium has some industrial purposes, but in combination with Beryllium it can be used to ensure the chain reaction leading to a nuclear explosion.

"It does heighten suspicions because Polonium-210 is so linked to a certain type of neutron-initiator," David Albright, an expert on nuclear proliferation at the Institute for Science and International Security told the daily.

"But it's not an ideal neutron-initiator. It doesn't last long, so you've got to keep producing it," he said.