Iran’s sole nuclear power plant has undergone an unexplained temporary emergency shutdown.

An official from the state electric company Tavanir, that the Bushehr plant shutdown began on Saturday and would last “for three to four days.”

The company has warned that the nation now faces power outages.

This is the first time Iran has reported an emergency shutdown of the plant in the southern port city of Bushehr.

The plant went online in 2011 with help from Russia.

Iran is required to send spent fuel rods from the reactor back to Russia as a nuclear nonproliferation measure.

Tavanir released a statement stating that the nuclear plant was being repaired. The company did not offer any further details but confirmed the repair work would take until Friday.