Tesla Inc (NASDAQ: TSLA) CEO Elon Musk is reportedly under investigation by federal authorities over his bid to purchase Twitter Inc (NYSE: TWTR).

What Happened: Twitter said in a court filing released Thursday that Musk's attorneys claimed "investigative privilege" while refusing to hand over material sought by the social media company, reported Reuters.

The lawyers had reportedly provided a "privilege log" to Twitter in September, which identified documents to be withheld.

The logs made reference to a May 13 email to the U.S. Securities and Exchange Commission and a slide presentation to the Federal Trade Commission, according to the report.

Musk attorney Alex Spiro said the court filing was a "misdirection" and said, "It is Twitter's executives that are under federal investigation," reported Reuters.

Twitter, the SEC and FTC did not immediately respond to Benzinga's request for comment.

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Why It Matters: The court filing was made on Oct.6, the same day the judge in the court case involving Twitter and Musk halted litigation between them after Musk reactivated the deal to buy the company.

Twitter had sued Musk in July to force a buyout after he walked out of a deal to take the company private at $54.20 per share.

The SEC had reportedly asked Musk in a letter in June whether he should have amended his public filing to indicate his intent to suspend or abandon the Twitter deal.

In April, The Information reported that Musk's $44 billion purchase of Twitter was under FTC scrutiny over antitrust reporting requirements.

Price Action: Shares of Tesla rose 2% on Thursday, before falling 0.5% to $220.6 in extended trading, while Twitter gained 0.9% to $50.39 before losing 0.1% in the after-hours session.

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