Iran's Natanz nuclear site has suffered a problem involving its electrical distribution grid just hours after starting up new advanced centrifuges that more quickly enrich uranium, state TV reports.
It was the latest incident to strike one of Tehran's most-secure sites amid stalled negotiations over the tattered nuclear accord with world powers.
State TV quoted Behrouz Kamalvandi, a spokesman for Iran's civilian nuclear program, announcing the incident on Sunday.
Kamalvandi said there were no injuries or pollution cause by the incident.
The Farsi word state television used in its report attributed to Kamalvandi can be used for both "accident" and "incident."
It did not immediately clarify the report, which ran at the bottom of its screen on its live broadcast.
Natanz suffered a mysterious explosion in July that authorities later described as sabotage.
Israel, Iran's regional arch-enemy, has been suspected of carrying out an attack there, as well as launching other assaults, as world powers negotiate with Tehran over its nuclear deal.
On Saturday, Iran announced it had launched a chain of 164 IR-6 centrifuges at the plant, injecting them with uranium gas and beginning their rapid spinning.
Officials also began testing the IR-9 centrifuge, which they say will enrich uranium 50 times faster than Iran's first-generation centrifuges, the IR-1.
The previously agreed nuclear deal limited Iran to using only IR-1s for enrichment.
Since then-president Donald Trump's withdrawal from the Iran nuclear deal in 2018, Tehran has abandoned all the limits of its uranium stockpile.
It now enriches up to 20 per cent purity, a technical step away from weapons-grade levels of 90 per cent.
Iran maintains its atomic program is for peaceful purposes, but fears about Tehran having the ability to make a bomb saw world powers reach the deal with the Islamic Republic in 2015.
The deal lifted economic sanctions on Iran in exchange for limiting its program and allowing inspectors from the International Atomic Energy Agency to keep a close watch on its work.
On Tuesday, an Iranian cargo ship said to serve as a floating base for Iran's paramilitary Revolutionary Guard forces off the coast of Yemen was struck by an explosion, likely from a limpet mine.
Iran has blamed Israel for the blast, with the attack simply the latest in a long-running shadow war targeting shipping in the region.