The U.S. government has opened a formal investigation into electric vehicle maker Tesla’s autopilot system after almost a dozen crashes.

The probe by the National Highway Traffic Safety Administration (NHTSA) covers an estimated 765,000 Tesla Model Y, X, S and 3 vehicles from the 2014 model year onward. The regulator, which has the power to deem cars defective and order recalls, said it launched the investigation after 11 crashes that resulted in 17 injuries and one fatality.

Tesla (NASDAQ:TSLA) shares fell 4.9% to $682.04 U.S. after the government investigation was announced.

Autopilot is Tesla’s driver-assistance system that maintains vehicles’ speed and keeps them centered in lanes when engaged, though the driver is supposed to always supervise. Since late 2016, Tesla has marketed higher-level functionality called “Full Self-Driving Capability” that sells for an extra $10,000 U.S. or a $199 U.S. per month subscription.

The NHTSA said it is looking at accidents in which one of two Tesla systems — Autopilot or Traffic Aware Cruise Control — was engaged.

The first of the 11 crashes that prompted the probe occurred in January 2018 in Culver City, California, according to NHTSA. The most recent accident occurred July 10 of this year in San Diego. Other accidents have occurred in Florida, Michigan, Texas, Arizona, Massachusetts, Indiana and Connecticut.