Iranian authorities are investigating a large explosion just east of the capital, Tehran, near a military base thought to have played a role in the country’s past nuclear testing activities.

Videos and pictures posted on social media that were picked up by local news outlets showed a bright light flaring out across the sky over the city early on Friday, followed by a large plume of smoke. Witnesses said the blast came from the direction of Parchin, a major military site.

Defence ministry spokesman Davoud Abdi told state TV the blast happened at a gas storage facility in a “public area” of Parchin rather than the military base. The fire had been put out and no casualties had been reported, he added, but gave no details about the cause of the blast.

“Our colleagues are present on the ground and investigating the incident carefully,” Abdi said.

Parchin is home to a sprawling military base where Iranian technicians were alleged to have tested high explosive components for a nuclear warhead in the early 200s, a claim Iran has denied.

In 2014, the military site was suspected to have been damaged by a fire or explosion but investigations by the International Atomic Energy Agency were hampered by a lack of access.

This is a developing news story, please check back for updates.