A satellite image has captured apparently extensive damage from an explosion at a military base near Tehran earlier this month.
Some buildings at the Revolutionary Guards base seem to have been completely destroyed in the explosion.
The 12 November blast killed 17 soldiers and has been widely blamed in Iran on foreign intelligence services.
On Monday, another in a series of unexplained explosions was reported in central Isfahan province.
They come at a time of heightened tensions over Iran's nuclear ambitions.
US and European powers fear that Iran is trying to develop a nuclear weapon, though Iran says its nuclear programme is purely for peaceful purposes.
There has also been speculation in Israel's media that Prime Minister Benjamin Netanyahu is considering ordering strikes against Iran's nuclear sites, in the hope of stalling or ending its programme.'Missile work'
The 12 November blast, which occurred about 40 km (25 miles) away from Tehran, was described at the time by the Revolutionary Guards as an accident, while one local member of parliament said an ammunition depot had exploded.
An elite military force, the Revolutionary Guard was set up shortly after the 1979 Iranian revolution to defend the country's Islamic system.
It has been targeted by UN sanctions aimed at pressuring Iran to halt uranium enrichment.
The images of damage at the site were released by the Washington-based Institute for Science and International Security.
It reported that when the explosion had happened, Iran was "apparently performing a volatile procedure involving a missile engine".
One of those killed was Gen Hassan Tehrani Moghaddam, who was said to have been working on Iran's missile programme.
Some damage seen in the image may have been caused by subsequent controlled demolition of buildings and removal of debris, the institute said.
On Monday, people in Isfahan told the BBC they had heard an explosion from the south-west - some distance from the province's declared nuclear facilities in the east.
Iranian media reports quoted the deputy governor-general of Isfahan province as confirming, then denying, that there had been an explosion.