An incident at Natanz nuclear complex in Iran caused significant damage and could slow the production of advanced centrifuges used to enrich uranium, the country's atomic energy spokesman said.
A mysterious explosion or fire occurred in one of the buildings at the sprawling nuclear facility on June 2, which destroyed a large part of a building.
Speculations range from internal sabotage to a cyberattack or a strike by Israel.
Iran maintains there were no casualties or radioactive fallout from the incident.
The country’s top national security council announced June 3 that the cause has been pinpointed but for security reasons the government will not disclose it. But Iran’s nuclear chief was quoted as saying June 5 that “various scenarios” are being examined as to what cause the incident.
"There were no victims... but the damage is significant on a financial level," Iranian Atomic Energy Organization spokesman Behrouz Kamalvandi said in an interview published Sunday by state news agency IRNA.
"In the medium term, this accident could slow down the development and production" of advanced centrifuges, he said. Natanz is one of Iran's main uranium enrichment plants.
"God willing, and with constant effort... we will compensate for this slowdown so that the rebuilt site will have even more capacity than before," Kamalvandi added.
The organization had earlier released a photo purportedly from the site, showing a one-story building with a damaged roof, walls apparently blackened by fire and doors hanging off their hinges as if blown out from the inside.
State TV later showed the building from a different angle with minor damage to its walls.
A satellite image published July 5 by Iran International TV based in London shows most of the building ruined as a result of the incident.
Tehran announced in May last year it would progressively suspend certain commitments under the 2015 nuclear agreement, including boosting uranium enrichment. Later it announced the deployment of advanced centrifuges to speed up enrichment. This could shorten the weaponization time if Iran intends to build a nuclear bomb.
Tehran has always denied its nuclear program has any military dimension, but regional countries, the United States and Western Europe have deep concerns..