Iran’s sole nuclear power plant has undergone an unexplained temporary emergency shutdown, state TV reported on Sunday.

An official from the state electric energy company, Gholamali Rakhshanimehr, said on a talk show that the Bushehr plant shutdown began on Saturday and would last “for three to four days”.

He said that power outages could result. He did not elaborate but this is the first time Iran has reported an emergency shutdown of the plant, located in the southern port city of Bushehr. It 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.

In March, nuclear official Mahmoud Jafari said the plant could stop working since Iran couldn't procure parts and equipment for it from Russia due to banking sanctions imposed by the US in 2018.

Bushehr is fuelled by uranium produced in Russia, not Iran, and is monitored by the United Nations’ International Atomic Energy Agency (IAEA). The IAEA did not immediately respond to request for comment on the reported shutdown.

Construction on Bushehr, on the coast of the northern reaches of the Persian Gulf, began under Iran’s shah in the mid-1970s. After the 1979 Islamic Revolution, the plant was repeatedly targeted in the Iran-Iraq war. Russia later completed construction of the facility.

The plant, which sits near active fault lines and was built to withstand powerful quakes, has been periodically shaken by temblors. There have been no significant earthquakes reported in the area in recent days.