A fire has consumed a centrifuge assembly plant located in the underground Natanz nuclear site of Iran on Thursday. Online video and messages have claimed responsibility for the incident were spread on Friday, deepening the mystery surrounding the blaze.

The Iranian capital, however, announced that it had knowledge of the source of the fire but refused to reveal details for reasons of national security, as reported by AP News.

A cyberattack?

The group claiming responsibility for the incident is a group known as "Cheetahs of the Homeland" and featured language that was native to multiple different organizations that opposed Iran. The group also emphasized on Iran's nuclear program and how its presence threatens the Israelite.

The Atomic Energy Agency of Iran (AEOI) denied the incident was caused by sabotage and later revealed an image that showed the area and the destruction that was caused by an apparent explosion. It could be seen in the footage that some parts of the structure were blackened.

The extent of the damage below the ground, however, remains unclear, as the Iranian government previously released videos which suggest most of the work is focused on advanced centrifuges which are responsible for purifying uranium.

One Middle Eastern intelligence official, who wished to remain anonymous, spoke out about highly-classified information that an explosive device was responsible for the blast that promulgated from inside the facility.

According to The New York Times, the source noted the explosion ruined most of the parts of the building located above the ground that housed the centrifuges while they were being balanced before being used.

Also Read: World War 3 Looms as Iran Rattles Sabers With the US in a Heated Row in the Middle East

The destroyed structure was located directly adjacent to the underground fuel production facilities that the United States and Israel used to operate modern times' most sophisticated cyberattacks ten years ago that were named "Olympic Games."

The attack continued for several years, misconfigured Iran's industrial equipment computer code and sabotaged nearly 1,000 centrifuges, pushing Iran's nuclear program back for at least a year, if not more.

What is more likely?

Despite the group claiming responsibility for the fire, the CISO at Cyjax, Ian Thornton-Trump, believes the incident is just a mere accident. He notes that a cyberattack would be qualified to conduct the strike but that it was much more likely it was a result of an accident or employee safety issue.

Thornton-Trump, however, added the actual reason behind the incident could not be determined as evidence would have to be provided before a conclusion can be reached, as reported by Forbes.

A former colonel with the British military intelligence, Philip Ingram, noted that a physical attack most likely caused the incident, but that cyberattack should still be taken into consideration.

Ingram emphasizes that Western cyber agencies have become much more aggressive with how the US is targeting Iranian air defence systems after Iran shot down one of America's spy drones last year.

The former colonel also said it is too early to conclude any facts about the incident but that Iran would surely be investigating the destruction of one of its most sensitive nuclear sites.

Related Article: What Israeli Defense Technology Can Do to Stop Iran's Small Attack Boats