The US Department of Justice has opened an investigation into Tesla's driver-assistance features, the company said Tuesday in a financial document.

The filing comes amid an ongoing National Highway Traffic Safety Administration (NHTSA) review of the electric carmaker's "Autopilot" system.

Tesla CEO Elon Musk has regularly promised that a fully autonomous vehicle is just around the corner, but his cars still only feature "driving assistance" -- which helps drivers change lanes or identify stop signs -- and not full autonomy that would allow drivers to look away from the road.

The company did not say what exactly the requests were, but according to media reports, the department is looking into whether Tesla's claims about the reliability of its driver assistance systems could leave drivers with a false sense of security.

This is not the first time Tesla's public marketing statements have come under regulatory scrutiny.

On its website, Tesla says its Autopilot and its Full Self Driving Capability options "require a fully attentive driver, who has their hands on the wheel and is prepared to take over at any moment."

But National Transportation Safety Board (NTSB) Chairwoman Jennifer Homendy in 2021 told CNBC that using the term "full self-driving" is "misleading."

According to a report from Bloomberg, the Justice Department investigation has been opened for similar reasons.

The NHTSA's probe includes investigations into several safety incidents associated with the driver assistance systems.

"To our knowledge no government agency in any ongoing investigation has concluded that any wrongdoing occurred," Tesla said in its Tuesday filing.