Two diplomats say Iran's only nuclear power plant, which already has raised safety concerns, has been damaged by recent earthquakes.
The unidentified diplomats told the Associated Press that international monitors believe large cracks have developed in one part of the Bushehr plant.
Iran has refused to join a global treaty on nuclear plant safety and Bushehr has been shut down several times since it opened in 2011.
Iran's neighbors, including Kuwait and Saudi Arabia, have said they are concerned about the safety of the Russian-built nuclear reactor.
Iran has insisted Bushehr is safe and says it was built to hold up in all but the most powerful of earthquakes.
Several earthquakes struck Iran in April and May, including a 7.7-magnitude quake. Bushehr was built to generate power and the West is not concerned that it could contribute to Iran's suspected nuclear weapons program.