An explosion has been heard over the northwest of Isfahan, a city in central Iran, the Iranian semi-official FARS news agency reported early Friday morning, citing local sources.

The cause of this explosion is still unknown.

Flight tracking website, Flight Radar 24 showed that multiple flights were diverted over Iranian airspace early Friday.

Videos reportedly from Isfahan appeared to show Iranian air defenses activated in the skies over the area.

The Iranian semi-official Fars News Agency reported that an explosion was heard in Qahjavarestan, east of Isfahan and near the Isfahan International Airport.

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