An explosion that shook Iran’s capital came from an area in the eastern mountains which analysts believe hides an underground tunnel system and missile production sites, satellite photographs show.
What exactly was blown up in the incident early on Friday which 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 blast, however, underlines the sensitive nature of the area near where international inspectors believe the Islamic Republic carried out high-explosive tests two decades ago for nuclear weapon triggers.
The explosion shook homes, rattled windows and lit up the horizon in the Alborz Mountains early on Friday. State TV later aired a segment from what it described as the site of the blast.
One of its journalists stood in front of what appeared to be large, blackened gas cylinders, although the camera remained tightly focused and did not show anything else around the site.
Defence Ministry spokesman Davood Abdi blamed the blast on a leaking gas he did not identify and said no-one was killed.
He described the site as a “public area”, raising the question of why military officials and not civilian firefighters would be in charge. The state TV report did not answer that.
Satellite photos of the area, some 12.5 miles (20km) east of central Tehran, showed hundreds of yards of charred scrubland not seen in images of the area taken in the weeks before the incident. The building near the char marks resembled the facility seen in the state TV footage.
The gas storage area is close to what analysts describe as Iran’s Khojir missile facility.
The explosion appears to have struck a facility for the Shahid Bakeri Industrial Group, which makes solid-propellant rockets, said Fabian Hinz, a researcher at the James Martin Centre for Nonproliferation Studies at the Middlebury Institute of International Studies in Monterey, California.
The Washington-based Centre for Strategic and International Studies identified Khojir as the “site of numerous tunnels, some suspected of use for arms assembly”. Large industrial buildings at the site visible from satellite photographs also suggest missile assembly being carried out there.
The US Defence Intelligence Agency says Iran overall has the largest underground facility programme in the Middle East.
Such sites “support most facets of Tehran’s ballistic missile capabilities, including the operational force and the missile development and production programme”, the DIA said in 2019.
Iranian officials themselves also identified the site as being in Parchin, home to a military base where the International Atomic Energy Agency previously said it suspects Iran conducted tests of explosive triggers that could be used in nuclear weapons.
Iran has long denied seeking nuclear weapons, though the IAEA previously said Iran had carried out work in “support of a possible military dimension to its nuclear programme” which largely halted in late 2003.
Western concerns over the Iranian atomic programme led to sanctions and eventually to Tehran’s 2015 nuclear deal with world powers.
The US under President Donald Trump unilaterally withdrew from the accord in May 2018, leading to a series of escalating attacks between Iran and the US, and Tehran abandoning the deal’s production limits.
Iran’s missile and space programmes have suffered a series of explosions in recent years.
The most notable came in 2011, when a blast at a missile base near Tehran killed Revolutionary Guard commander Hassan Tehrani Moghaddam, who led the paramilitary force’s missile programme, and 16 others.
Initially, authorities described the blast as an accident, though a former prisoner later said the Guard interrogated him on suspicion that Israel caused the explosion.