The U.S. auto safety regulator has deepened a probe into Tesla’s driver-assistance system to evaluate its effectiveness ​in identifying degraded road conditions after nine crashes linked ‌to the technology including one that was fatal.

The probe covers roughly 3.2 million vehicles, across multiple models, accounting for nearly all vehicles the company has sold ​in the United States.

The move marks a significant escalation that ​could lead to a recall or other enforcement action ⁠if regulators find a safety defect.

Tesla’s ambitions to deploy fully autonomous ​vehicles and robotaxis hinge on the reliability and safety of its ​Full Self-Driving (FSD) system, which remains under regulatory scrutiny.