The National Highway Traffic Safety Administration (NHTSA) has opened an investigation regarding the potential safety issue of several Tesla models braking unexpectedly while using AutoPilot, reports CNN.

Known as “phantom braking,” the braking happens without warning and often repeatedly in a single drive.

The investigation covers 2021-22 Tesla Model 3s and Tesla Model Ys. NHTSA believes approximately 416,000 vehicles may be affected by this safety issue.

However, the agency did not say whether it was aware of any collisions, injuries, or fatalities associated with the problem, notes CNN.

According to several reports, NHTSA's Office of Defects Investigation said it has received 354 complaints in the past nine months for unexpected brake activation. The random braking occurs while using Autopilot, Tesla’s suite of driver-assist features, which allow the vehicle to brake and steer automatically.

This latest probe comes on the heels of a series of safety recalls issued by Tesla as well as two recent safety investigations by NHTSA. Specifically, one probe concerned Tesla models equipped with “Passenger Play,” which originally allowed the video games to be played on a screen mounted on the dashboard while the vehicle was in motion. The second NHTSA investigation concerned Tesla’s Autopilot system, which occurred after a series of crashes in vehicles that use the system.  

Most NHTSA investigations start as preliminary evaluations whereby the agency gathers information from the automaker such as data on complaints, injuries, and warranty claims. After this phase, NHTSA will either close the investigation or move into the next stage. If a safety-related defect exists, the agency may send a "recall request" letter to the carmaker.