Elon Musk has earned plaudits for Tesla’s work to help Ukraine stay online during its war with Russia, but it has been reported that his company has also done business with a sanctioned Russian oligarch.

On Monday, CNBC reported that since 2020 Tesla has purchased millions of dollars in aluminum from Rusal, one of the largest aluminum companies in the world. Rusal is led by one of Russia’s most prolific oligarchs, Oleg Deripaska, who is close to Russian President Vladimir Putin.

According to internal documents seen by CNBC, Tesla purchased aluminum from Rusal for casting parts at a vehicle assembly plant outside of Berlin, Germany. The plant in question is not yet fully operational.

There does not appear to be evidence that Russian aluminum has been used to construct cars sold in the U.S. The documents also do not specify whether or not any business relationship remains active.

Neither Musk nor the company has commented on the CNBC report.

Rusal came under U.S. sanctions in April 2018 under the Trump administration. Deripaska is said to be Putin’s “favorite industrialist.”

Tesla’s arrangement with Rusal is not especially unique. As one of the world’s largest aluminum companies, it has maintained commercial ties to firms worldwide, including in the U.S.

Beyond his stature in Putin’s eyes, Deripaska is well-known for his relationship with Paul Manafort, who served as one of former President Donald Trump’s campaign managers in 2016. According to The New York Times, Deripaska was approached by the FBI between 2014 and 2016 to request he help provide any information related to Russian organized crime or on any links between the Kremlin and its interference in the 2016 presidential election. Deripaska rebuffed the agents and maintains that he has no knowledge of any efforts to influence the election.

A home belonging to the Russian billionaire in Washington D.C. was raided last October by FBI agents, but it remains unclear why he came under investigation.

Musk has earned praise for his efforts to support Ukraine since it came under Russian attack on Feb. 24. After Ukraine’s Minister for Digital Transformation Mykhailo Fedorov called on Musk to keep his country online on Feb. 28, the Tesla CEO confirmed his Starlink service would provide internet.

Tesla also said that the company would pay Ukrainian employees who are drafted to fight in the war for three months. Around 5,000 Tesla workers are based in Ukraine.