Experts say ‘deeply’ concerned over Iran’s work at underground nuclear site

close Video Analyzing strikes on Kharg Island: The key to Iran's oil economy Retired Navy Captain Brent Sadler joins 'Fox News Sunday' to break down the strategic importance of Kharg Island and the operational challenges of neutralizing 'Pickaxe Mountain,' a nuclear facility deeper than any previously struck Iranian site. NEWYou can now listen to Fox News articles! Hören Sie sich diesen Artikel an 4 Min One of the leading American institutes devoted to research on the Islamic Republic’s nuclear program sounded the alarm this week over the regime's uninspected underground site in the Zagros Mountains. Inspectors from the International Atomic Energy Agency (IAEA) have not been allowed to visit the secret site, known as Pickaxe Mountain. The highly secretive facility is casting serious doubt on Iran’s willingness to abide by the terms of the memorandum of understanding (MOU) reached with the Trump administration. The United States, together with Israel, launched Operation Epic Fury on February 28, 2026, targeting Iran’s nuclear and missile capabilities. Experts from the Washington-based Institute for Science and International Security (ISIS) argue that halting work at Pickaxe Mountain and allowing IAEA inspectors access would be a key good-faith measure to test whether Iran is prepared to abandon its pattern of deception. OBAMA-ERA INSPECTION FLAWS IN Iran COULD PERSIST AS EXPERTS WARN OF NUCLEAR BLIND SPOTS Satellite image shows an overview of the Pickaxe Mountain tunnel complex in Natanz. (Vantor/Handout via REUTERS) Spencer Faragasso, a senior fellow with group who covers Iran, North Korea, illicit trade, and nuclear issues, wrote on X: "Important update by us at @TheGoodISIS. The ongoing work at Pickaxe Mountain is deeply concerning. This work has continued steadily since at least 2020. In my view, this is a hedge by Iran in case negotiations fail — they will then have a nuclear facility in a late stage of construction. We assessed that Pickaxe is likely large enough to hold an enrichment plant." Iran has used facilities at Natanz, Fordow and Isfahan to enrich uranium, the key material for a nuclear weapons program. Faragasso added, "If Iran is serious about negotiating, it should halt construction at Pickaxe Mountain as a token of good faith. But what can be expected from a regime as brutal and conniving as Iran’s?" The institute posted a detailed analysis of new satellite imagery from late June 2026 showing continued activity at Pickaxe Mountain. Trump administration UNVEILS SWEEPING TERMS OF PROPOSED Iran AGREEMENT Vice President JD Vance prior to a quadrilateral meeting between the United States, Iran, Pakistan and Qatar at the Burgenstock luxury hotel complex overlooking Lake Lucerne, Switzerland, on Sunday June 21, 2026. (Fabrice Coffrini/Keystone via AP) The institute wrote that "at Pickaxe Mountain, vehicle activity can be seen on the roads leading to the open set of Western tunnel portals, indicating that construction inside the tunnel complex, as well as hardening of the tunnel entrance, are ongoing. The MOU signed between the United States and Iran requires that Iran maintain the status quo, which should prohibit construction at any nuclear-related facility, including Pickaxe Mountain." In late June, the IAEA declined to answer a detailed Fox News Digital query on whether it would seek access to the Pickaxe Mountain facility. According to the satellite imagery obtained by the institute: "At Natanz, little activity can be seen. The access points to the below-ground enrichment halls have not been repaired. The personnel entrances remain destroyed and vehicle entrances remain severely damaged. A single vehicle can be seen on the road outside of the Pilot Fuel Enrichment Plant (PFEP), which was destroyed in June 2025 but was later covered by Iran." As U.S.-Iran talks opened Sunday in Switzerland, a dispute over who controls and monitors billions of dollars in potentially unfrozen Iranian assets emerged (Fabrice Coffrini/Pool via REUTERS) The institute also reported: "As of June 29, 2026, there is no observed activity at Esfahan. The tunnel portals remain backfilled with dirt." ISIS tracked developments at the Fordow site, buried inside a mountain north of the holy Islamic city of Qom. "At Fordow, as earlier reported by the Institute, between May 10 and May 18, Iran added passive defensive measures in the form of earthen/rocky mounds and other objects on the roads leading to the tunnel entrances. The alternating placements of the piles/objects are very precise, which creates a series of chicanes, indicating they are not intended as obstructions but rather to prevent rapid ingress and egress by any vehicle toward the tunnels." The institute added, "The June 21 Vantor image shows that the objects along the road remain there. The tunnel portals also remain backfilled with dirt," at Fordow. Fox News Digital sent questions to the State Department and the Iranian Mission to the United Nations. Benjamin Weinthal reports on Israel, Iran, Syria, Turkey and Europe. You can follow Benjamin on Twitter @BenWeinthal, and email him at benjamin.weinthal@fox.com