The Atomic Energy Organization of Iran (AEOI) shared a picture of the damaged building, which appeared to show a roof charred by fire, broken doors and blown windows.
The thermal signature of the fire appears to have been captured by the NOAA-20 satellite, operated by the National Oceanic and Atmospheric Administration (NOAA). The fire was detected in the northwest corner of the facility at approximately 2:06 a.m. local time early Thursday morning, according to data obtained by CNN from the satellite.
No casualties have been reported at facilities in the Iranian province of Isfahan, south of the capital Tehran, according to the semi-official Tasnim news agency.
The incident is under investigation, according to state media, Press TV, which quoted an anonymous Iranian security official as saying that there was "no evidence" of sabotage.
Questions swirl in the international community about the incident, which comes just a week after a major explosion on the outskirts of Tehran, near the city of Parchin and a military installation.
Yassamine Mather, a researcher at the Middle East Center at the University of Oxford, told CNN that the incident was "very strange".
Ramazanali Ferdowsi, the governor of Natanz, said the fire only damaged one building under construction in the complex and did not affect the main area of the nuclear facility, Tasnim reported.
The incident did not disrupt ongoing activities at the site, said an AEOI spokesperson, Behrouz Kamalvandi, according to IRNA.
"Teams of AEOI experts have been deployed to investigate the factors leading to damage to the prefabricated steel structure," said Kamalvandi.
He told Press TV that the incident had not "stopped" the enrichment works at the facility, which are "mainly carried out underground".
He also dismissed the possibility that the incident may have resulted in possible radioactive contamination. "Contrary to the false propaganda of the enemy and counter-revolutionary media, no contamination occurred because there was no nuclear material in this hangar," he told Press TV.
