Iran's Defense Ministry says there has been an explosion at an Iranian gas-storage facility in an area with a sensitive military site to the east of Tehran.
The explosion took place in the "public area" of Parchin rather than the military site, Defense Ministry spokesman Davoud Abdi told Iranian state TV on June 26.
Western intelligence services believe Tehran had carried out tests at the military site more than a decade ago that were relevant to the development of nuclear weapons. Iran denies those reports.
Abdi said a fire caused by the explosion was brought under control and that there were no casualties. He did not provide any information about the cause of the explosion.
But the Fars news agency, which is close to Iran's Islamic Revolutionary Guards Corps (IRGC) quoted what it called "an informed source" as saying a gas storage tank had exploded near a military base.
According to Fars, the source emphasized that the explosion had nothing to do with the military base itself.
It also said police were investigating the blast.
The Mehr News Agency issued a brief news alert saying a loud sound was heard in eastern Tehran.
Mehr also quoted an official of Iran's emergency services saying that no requests for ambulances or emergency assistance had been received from the area.
Videos and pictures posted on social media were picked up by local news outlets. They show an explosion with a bright orange flash occurring to the east of Tehran shortly after midnight on June 26.
The flash was followed by a large plume of smoke.
One social media channel known to be close to the Quds Force, a special forces unit within the IRGC that is responsible for operations outside of Iran, initially reported that the explosion was at Parchin.
But it later retracted that report and said the blast had taken place in Khojir in the same area.
Iranian authorities do not quickly and accurately report security-related incidents.