NASA Administrator Bill Nelson has called for an investigation into Elon Musk’s communications with the Kremlin after a Wall Street Journal report found that the billionaire X CEO and Trump donor has been regularly communicating with Russian President Vladimir Putin since late 2022.

“I don’t know that that story is true,” Nelson told Semafor on Friday. “I think it should be investigated. If the story is true that there have been multiple conversations between Elon Musk and the president of Russia, then I think that would be concerning, particularly for NASA, for the Department of Defense, [and] for some of the intelligence agencies.”

NASA partners with SpaceX, which Nelson praised as “phenomenally successful.”

The news about a close Musk-Putin relationship comes not long after it reported that Donald Trump himself has also been talking with Putin since leaving office.

According to journalist Bob Woodward, Trump has had as many as seven conversations with the Russian president since early 2021. This was also the time period when Trump, as the Justice Department alleges, was in possession of classified national security documents.