The loud explosions heard in numerous regions of western Iran early Sunday were caused by lightning, not foreign military assaults, according to a semi-official Iranian news outlet quoting a military source.

According to Iranian official media and social media posts, loud explosions were heard in at least four of Iran’s western provinces – Hamadan, Kurdistan, Kermanshah, and Ilam – at midnight local time on Sunday.

Lightning was the primary cause of the bombings in western Iran, according to a “informed source” in the Iranian armed forces, according to the semi-official Tasnim news agency.

“The authority also dismissed various internet hypotheses linking the noises reported to sabotage and foreign strikes,” Tasnim wrote.

Tasnim’s revelation came only hours after a local governor in Hamadan province ruled out the possibility that the blasts were caused by lightning.

“Initially, it was assumed to be the sound of thunderstorms owing to the meteorological circumstances,” said Saeed Ketabi, governor of the city of Asadabad, according to the semi-official Fars news agency.

Several such events have lately been linked by Iranian officials to unannounced military drills, as tensions with Israel and the US over Iran’s nuclear program have risen.

Israel has warned that if diplomacy fails to prevent Iran from gaining nuclear weapons, it will resort to military. Tehran claims that its nuclear program is only for peaceful purposes.

The United States and Iran are now holding indirect discussions in Vienna to resurrect the 2015 Iran nuclear agreement, which Washington withdrew from in 2018 under then-President Donald Trump, reimposing harsh penalties on Tehran.

Iran has subsequently begun enriching uranium to 60 percent purity, bringing it one step closer to the 90 percent required for weapons-grade material.

In exchange for sanctions relief, Iran agreed to curtail its nuclear development under the 2015 agreement.