Sen. Elizabeth Warren urged the Securities and Exchange Commission to investigate whether Tesla violated regulations over board independence at public companies, the Wall Street Journal reported Thursday, citing a letter.

The letter sent this week by the Massachusetts Democrat — and frequent critic of Tesla boss Elon Musk — also raised concern about potential conflicts of interest between the automaker and the private companies that Musk operates, according to the report.

Tesla did not immediately respond to a Reuters request for comment.

Separately, in a letter to SEC Chair Gary Gensler in July, Warren called on the regulator to open an investigation into Tesla and its board’s failure to manage Musk’s actions in his dual role then, as CEO of Twitter, now called X, and the automaker.