An explosion that rattled Iran’s capital came from an area in its eastern mountains that analysts believe hides an underground tunnel system and missile production sites, satellite photographs showed Saturday. What exploded in the incident early Friday that sent a massive fireball into the sky near Tehran remains unclear, as does the cause of the blast. The unusual response of the Iranian government in the aftermath of the explosion, however, underscores the sensitive nature of an area near where international inspectors believe the Islamic Republic conducted high-explosive tests two decades ago for nuclear weapon triggers.