Iran Blocks Access Roads to Underground Nuclear Facility Near Natanz

New satellite imagery reveals that Iran has blocked access roads to the western tunnels at the Kuh-e Kolang Gaz La underground facility near Natanz with mounds of earth, according to information obtained on Tuesday.

Satellite Evidence and Defense Measures

According to the Institute for Science and International Security (ISIS), the move was carried out following threats by U.S. President Donald Trump to strike the site and reports that centrifuges were transferred into it. Iran placed a series of dirt piles across the roads leading to the two western tunnel entrances between late July and early August. The blockages were visible in a satellite image from August 21 and remained in place on September 11. Institute researchers assess that this is a defensive measure designed to prevent rapid entry and exit of vehicles through the tunnel openings.

The blockade significantly limits Iran's ability to conduct construction work or other activities inside the subterranean facility.

Expanding Restrictions Across All Entrances

The step comes after reports in late July that Iran transferred centrifuges to the facility following the conflict in June 2025. During that period, President Donald Trump publicly threatened that the United States might strike Kuh-e Kolang Gaz La, which is considered one of the primary remaining sites of the Iranian nuclear program that has not been damaged in previous strikes.

According to institute analysts, this is not the first blockade of the complex's entrances. Photographs from April and May showed that Iran also partially filled two eastern tunnel openings with earth. Following the blocking of the roads to the two western openings, it appears that all four entrances to the compound currently prevent vehicular traffic. Iran will be required to clear the earth barriers to renew ground access to the facility.