NASA’s monitoring system detected a powerful heat surge near Iran’s nuclear facility at Fordow shortly before the US announced its airstrike, The New York Times reports.

According to the outlet, one of the thermal signals was recorded about 30 minutes before President Donald Trump announced the strikes on Iran. Such signals are typically detected in areas of bombings or large-scale fires.

Although in some cases the system can pick up industrial emissions or natural fires, no such activity had been recorded near Fordow in the past month.