(Bloomberg) -- Federal Bureau of Investigation agents are searching the home of sanctioned Russian billionaire Oleg Deripaska in Washington, NBC News reported.

Deripaska, the founder of aluminum producers En+ Group and United Co. Rusal, has been blacklisted by President Donald Trump’s administration.

Earlier this year, a U.S. federal judge denied a lawsuit by Deripaska that sought to challenge the oligarch designation. U.S. had said Deripaska punishment is in response to Russia’s worldwide malign activities, which included occupying Ukraine’s Crimean peninsula, supplying weapons to the regime of President Bashar al-Assad of Syria and attempting to subvert Western democracies.

The reason for FBI’s search isn’t clear, NBC said. Rusal shares fell as much as 7.6%, the most since June, and were down 6.5% to 78.50 rubles at 12:10 p.m. New York.

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