Moscow: Russia’s Federal Security Service (FSB) is investigating the Moscow office of Alrosa in relation to non-core asset sales between 2011 and 2013.

The state-controlled Russian firm, which is the world’s largest producer of rough diamonds in carat terms, and the FSB both declined to comment, while the source who revealed the story did not provide any other details, Reuters reported.

Alrosa sold several non-core assets between 2011 and 2013, including a 51 percent stake in the Timir iron ore project to Evraz, a major Russian steelmaker. It also agreed to sell its gas assets to Russian oil giant Rosneft, but the two sides later failed to agree on the price.

The deals were done under former Alrosa Chief Executive Fyodor Andreev who held the post between 2009-2014. He died in 2015 after a long-term illness.

The Interfax news agency in Russia had earlier cited a source as saying law enforcement officials were removing documents from Alrosa’s Moscow office following a request from investigators in Russia’s far eastern Yakutia region, where its main production assets are based.