On August 7 Tesla CEO Elon Musk tweeted about taking the automaker private. While it may have seemed to slip out of the news, the tweet had not slipped the minds of federal agencies. 

The Wall Street Journal reported on Tuesday that the Department of Justice (DOJ) now has an open investigation into the Silicon Valley company, and whether it violated any rules when Musk sent his now-infamous tweet.

Tesla said it received from the agency a "voluntary request for documents," which is step one in an investigation.

A statement released by the automaker said, "we respect the DOJ's desire to get information about this and believe that the matter should be quickly resolved as they review the information they have received."

A spokeswoman from the DOJ told Motor Authority it "does not confirm, deny, or otherwise comment on the existence or non-existence of an investigation."

The criminal investigation joins an already ongoing inquiry by the SEC, which is looking into a variety of possible trade violations. A tweet such as Musk's could artificially raise the automaker's share value, for example.

Tesla also faces multiple lawsuits filed by investors who claim Musk's tweet manipulated the automaker's stock price in an effort to harm short sellers.

Since the initial tweet, Musk has said he will not take Tesla private.

Musk stated "funding secured" in the August 7 tweet, but waited until August 13 in a blog post on the company's website to announce the funding would come from the Saudi Arabian sovereign wealth fund. On Tuesday the Saudis invested $1 billion into Tesla rival Lucid Motors.