The sound of an apparent explosion was heard from Iran's Isfahan city on Monday afternoon, the head of the judiciary in the province said, according to Iran's ISNA news agency.
"In the afternoon, there was a noise like an explosion, but we don't have any information from security forces on the source of the noise," Gholamreza Ansari was quoted as saying.
An important Iranian nuclear facility involved in processing uranium is located near Isfahan city, although Iranian media reports of the incident did not say whether the explosion was near the nuclear centre.
Gill Tudor, spokeswoman for the International Atomic Energy Agency, said the UN watchdog was aware of the media reports but had no further information.
Iranian media provided contradictory information about the incident, which came less that three weeks after a massive explosion at a military base near Tehran that killed more than a dozen members of the Revolutionary Guard including the head of its missile forces.
The Fars news agency reported a large blast in the province but later removed the report from its website.
The Mehr news agency cited other Iranian news media, which it did not identify, as reporting that a blast had taken place at a petrol station at a town near Isfahan city. However, it also quoted the deputy governor of the province as saying he had no reports of a big explosion in his region.
"So far no report of a major explosion has been heard from any government body in Isfahan," Deputy Governor Mohammad Mehdi was quoted as saying by the semi-official news agency.
Several residents of the city contacted by Reuters by telephone said they heard nothing.
On Nov. 12, Iran said a massive explosion at a military base 45 km west of Tehran killed 17 Revolutionary Guards, including the head of the elite force's missile program. Iran said that explosion, which could be heard as far away as the capital, was caused by an accident while weapons were being moved.
Monday's report of the apparent blast near Isfahan attracted wide attention in Israel, which pays close attention to Iran's nuclear program. Israeli television stations led their evening news broadcasts with the reports.
None of the Israeli reports offered any comment from Israeli officials or provided any details beyond what the Iranian news agencies said. An Israeli military spokeswoman reached by telephone declined to comment on the reports.
Iran's Atomic Energy Organization operates several nuclear facilities east of Isfahan, according to the Institute for Science and International Security (ISIS), a leading Washington-based think tank.
They include the Uranium Conversion Facility (UCF), which began operating in 2006 and produces uranium hexafluoride gas, the feed material that Iran uses to make refined uranium at its Natanz nuclear enrichment site.
Israel and the West are concerned about Iranian processing of uranium, because they believe that it could be used to make a nuclear weapon. Iran says its nuclear program is peaceful.