Iran transferred thousands of uranium enrichment centrifuges to underground facilities deep inside Natanz’s Pickaxe Mountain last fall, The Wall Street Journal reported on Monday, citing Israeli and US officials.
The centrifuges were transferred to the mountain following the 12-day war in June 2025.
During the war, American and Israeli strikes pummeled three of Iran’s main nuclear sites, in an operation the US called “Midnight Hammer.”
US and Israeli officials noted that the transfer of sensitive equipment inside the mountain increases concerns that Tehran is working to ensure continued uranium enrichment, even in the event of a large-scale military attack on its soil.
Pickaxe Mountain is located south of the Natanz nuclear complex, the site of two of Iran’s uranium enrichment plants bombed in June 2025.
The tunnel facility under construction at Pickaxe Mountain wasn’t targeted in either of the wars, according to the Institute for Science and International Security (ISIS), a US-based think-tank focused on nuclear non-proliferation.
Satellite imagery shows that the complex was carved to a depth of more than 100 meters below bedrock, making it deeper and more fortified than the Fordow enrichment facility, a highly fortified, underground uranium enrichment facility.
Reaching depths in a mountain is a complex task
Reaching these depths is considered a complex task, even for the most advanced bunker-penetrating bombs in the US arsenal.
Tehran claimed that the site is intended solely as a factory for the production and assembly of advanced centrifuges, not as an active enrichment facility. Iranian authorities, however, are preventing International Atomic Energy Agency inspectors from entering the site.
IAEA Director-General Rafael Grossi demanded that Iran provide answers regarding its activities at the site. However, Iran failed to give answers that would allow the Iranian statements to be verified or the presence of nuclear material inside the mountain to be ruled out.
The relative immunity afforded by the rock’s depth has made the site one of the main targets in the confrontation with the United States.
US President Donald Trump threatened to eliminate the site, adding that his administration was closely monitoring activity surrounding the tunnel’s entrances.
Reuters contributed to this report.