Tesla shares declined following news of an investigation by the US National Highway Traffic Safety Administration (NHTSA), covering nearly 2.9 million vehicles equipped with the Full Self-Driving (FSD) system. The probe was launched after complaints about dangerous behavior — such as running red lights and unpredictable lane changes.

After the announcement, Tesla’s premarket stock fell by more than 3%, reflecting investor concerns over potential fines and recalls. The investigation could become the largest in the company’s history, as it involves nearly the entire Tesla fleet in the US.

Regulators noted that the FSD feature may allow autonomous actions beyond safe limits, increasing the risk of accidents. Tesla has previously faced criticism for exaggerated claims about the level of autonomy and insufficient driver oversight.

Investors fear that further scrutiny could slow the rollout of self-driving technology and negatively affect the company’s stock in the near term.