Images taken by commercial satellite firm Planet Labs of the Modarres military base in March and the Khojir missile production complex in April show more than 30 new buildings at the two sites, both of which are located near Tehran.

The images, reviewed by Reuters, show many of the structures are surrounded by large dirt berms. Such earthworks are associated with missile production and are designed to stop a blast in one building from detonating highly combustible materials in nearby structures, said Jeffrey Lewis of the Middlebury Institute of International Studies at Monterey.