Another owner of a Model Y said that while driving on a motorway “the car braked hard and decelerated from 80 mph to 69 mph in less than a second. The braking was so violent, my head snapped forward and I almost lost control of the car.”

Tesla, which disbanded its media relations department, did not respond to a request for comment on the probe.

The investigation is the latest in a string of enforcement efforts by the US auto safety regulators into autopilot and “self-driving” software.

Despite their names, neither feature can drive cars without a person supervising.

The preliminary investigation into “phantom braking” is the first phase before regulators can issue a formal recall demand.

It is also the fourth formal investigation of Tesla in the past three years.

In August, the NHTSA opened a formal safety probe into Tesla’s autopilot system in 765,000 cars after a series of crashes involving emergency vehicles.

In addition, the agency has sent investigators to at least 33 crashes involving Teslas using driver-assist systems since 2016 in which 11 people were killed.

Tesla has issued 10 recalls since October, including a recall of nearly 12,000 vehicles that month for a similar “phantom braking” problem.

Just last week, the electric car maker recalled nearly 579,000 vehicles in the US over its “Boombox” feature.

The feature enabled drivers to play sounds such as a bleating goat or a fart noise instead of a regular horn.

Regulators said it could impede pedestrians’s ability to hear warning sounds.

Tesla CEO Elon Musk said last week: “The fun police made us do it (sigh).”