An object exploded Saturday in the night sky near the Iranian nuclear facility in the town of Natanz, with state television saying it was a missile exercise.

Natanz’s governor said there were no casualties and that a report would be released Sunday. Initial reports said the explosion was a defensive strike against a hostile drone, but officials have denied this. Instead, they say it was a drill to test how quickly their defense missiles work. Locals reported a loud sound and a bright flash at around 9 p.m.