The Center for Strategic and International Studies said satellite images show that construction activity in the underground complex of Kalan (Kuh Kelang Gezla), near the Natanz nuclear facility, has increased significantly in 2026.

According to the report, activities have shifted from extensive drilling toward possible construction in internal sections and strengthening of tunnel entrances, and road activity has reached its highest level since construction of the complex began.

The center said the satellite images neither confirm nor refute Israel’s claim about the transfer of centrifuges and their components to Kuh Kelang Gezla. Analysts added that the complex is likely not yet ready for uranium enrichment.

Construction of this tunnel complex, two kilometers south of the Natanz facility, began in 2020. The International Atomic Energy Agency has called for access to it. U.S. President Donald Trump had also previously said that if activity in the complex is established, the United States could target it.