Why was there a massive explosion near Tehran in Iran?

Iran’s official story is that a gas storage facility had a minor accident and no one was harmed.

A display featuring missiles and a portrait of Iran's Supreme Leader Ayatollah Ali Khamenei is seen at Baharestan Square in Tehran, Iran September 27, 2017 (photo credit: NAZANIN TABATABAEE YAZDI/ TIMA VIA REUTERS)
A display featuring missiles and a portrait of Iran's Supreme Leader Ayatollah Ali Khamenei is seen at Baharestan Square in Tehran, Iran September 27, 2017
(photo credit: NAZANIN TABATABAEE YAZDI/ TIMA VIA REUTERS)
A massive explosion near Tehran lit up the sky on Thursday night, so brightly that it looked like the sun for a split second. Iran’s official story is that a gas storage facility had a minor accident  and no one was harmed. It was  “fortunate,” Iran’s official account says. Nothing to be concerned about. Video shows a small pipe had burst open and exploded.
Iran’s own Press TV showed the glowing explosion. There is a lot of speculation that the facility that exploded is more than just a gas leak. It has links to the Islamic Revolutionary Guard Corps and missiles. Others suggested it has links to a nuclear facility and the military. Villages near the facility were likely affected and residents may know more. All of this points to a questionable incident. 
A facility that just happens to be near one of Iran’s major areas for producing rockets and also linked to the country’s nuclear research and nuclear program? At the very least you don’t want those kinds of sensitive sites just blowing up without any clear explanation.
The explosion adds to the usual mystery of what goes on in Iran. Iranians are facing difficult economic times. They also had to deal with a cover-up by the government of COVID-19 threats. In addition, they have faced cyberattacks on a port in the South as well as other disputes. 
A massive explosion near Tehran adds to the concerns that the regime may be flailing about, or that sensitive areas, including those storing gas, are not properly monitored. Iranian citizens likely won’t get a full accounting of the explosions, just as the government in Tehran didn’t explain how it managed to mistakenly shoot down a civilian airliner earlier this year. The government also killed more than 1,000 protesters last year.
The obfuscation means it is difficult to believe Tehran’s assertions. Iran is building new missiles and says it is enriching nuclear material. It recently launched a military satellite. Conscientious online sleuths have looked for the area of the explosion, identifying a hillside east of Tehran. This area is between Shahid Lavasani Hospital and the Khojir National Park. 
The Khojir area houses a facility for making surface-to-surface missiles. These may be precision-guided munitions that are the kind trafficked to Hezbollah. This is also a pretty area and was once a royal hunting ground and one of the oldest officially protected areas near Tehran. If the explosion was merely gas facilities then the burn marks and video Iran’s media showed may be accurate. But it may also conceal a more unclear explanation for why these tanks suddenly exploded.