Iran's top security body said on Friday it had determined the cause of an "accident" at the Natanz nuclear site but declined to release details, AFP reported.
"Investigations by relevant bodies have accurately determined the cause of the accident at... Natanz nuclear complex," said a spokesman for Iran's Supreme National Security Council.
"Due to certain security concerns the cause and details of this accident will be announced at the proper time," state news agency IRNA quoted the spokesman, Keyvan Khosravi, as saying.
Iran on Thursday reported an "accident" at the Natanz nuclear complex in central Iran, saying there were no casualties or radioactive pollution.
Iran's Atomic Energy Organization gave no further details, but Natanz governor Ramezan-Ali Ferdowsi told the Tasnim news agency that a fire had broken out at the site.
Hours after the announcement on Thursday, IRNA published an editorial warning Iran's arch-foes against hostile actions, saying that unnamed Israeli social media accounts had claimed the Jewish state was behind the incident.
"If there are signs of hostile countries crossing Iran's red lines in any way, especially the Zionist Regime (Israel) and the United States, Iran's strategy to confront the new situation must be fundamentally reconsidered," the agency said.
On Friday, the Kuwaiti-based Al-Jarida newspaper reported that Israel was responsible for the fire at Natanz.
Iran's nuclear body has yet to provide an explanation for the cause of the incident, which came six days after an explosion near a military complex in Parchin area southeast of Tehran rocked the Iranian capital.
Authorities blamed that blast on "leaking gas tanks".
Tehran announced in May last year it would progressively suspend certain commitments under a 2015 nuclear deal with major powers after the United States withdrew from the deal.
Iran restarted enriching uranium at Natanz last September after having agreed under the accord to put such activities there on hold.
As for the Parchin site, Iran has denied that it is related to its nuclear program, though it did admit at one point to using Parchin to test exploding bridge wires, used as nuclear detonators.
(Arutz Sheva’s North American desk is keeping you updated until the start of Shabbat in New York. The time posted automatically on all Arutz Sheva articles, however, is Israeli time.)