NASA's monitoring system detected powerful heat radiation near Iran's Fordow nuclear facility shortly before the US announced the airstrike, The New York Times reported.
According to the agency, one of the heat signals was detected about 30 minutes before President Donald Trump announced the strikes against Iran. The system typically detects such signals at the sites of bombings or large-scale fires.
While in some cases the system can detect industrial emissions or forest fires, no such events have been detected in the Fordow area over the past month.
US President Donald Trump has warned Iran if it retaliates, threatening to use more force than during the last operation.
“Any retaliatory measures by Iran against the United States of America will be met with force far exceeding that demonstrated tonight,“ the head of state wrote on Truth Social.