The U.S. government opened an investigation into Tesla’s Autopilot partially-automated driving system. It claimed that it had difficulty spotting emergency vehicles parked.

This investigation includes 765,000 vehicles. It covers almost all Teslas sold in America since the beginning of 2014.

Monday’s announcement by the National Highway Traffic Safety Administration was posted on its website.

According to the agency, 11 accidents have been identified in which Teslas using Autopilot or Traffic Aware Cruise Control struck vehicles with flashing lights, flares, or illuminated arrow boards warning of dangers.

This investigation covers Tesla’s entire model line-up, including the Models Y and X as well as the Models S and 3 for the years 2014-2021.

Tesla drivers have often misused Autopilot, including driving drunk and riding in the backseat while their car rolls down California highways.

Since June 2016, the agency has sent 31 investigator teams to investigate crashes involving partially-automatic driver assistance systems. These systems keep vehicles centered in their lane and away from other vehicles. According to agency data, there were 25 crashes involving Tesla Autopilot, resulting in 10 deaths.

Tesla and other manufacturers advise that drivers who use the system must always be prepared to respond. The system has been used to crash into semis that were crossing in front of Teslas, stopping emergency vehicles and creating a road barrier.

An early Monday message sought to get clarification from Tesla. It has since closed its media relations office.

NHTSA cited two crashes into emergency vehicles in Culver city, California. The first was Jan. 22, 2018, when a Tesla using Autopilot collided with a parked firetruck partially in the travel lanes, its lights flashing. Crews were also handling another accident at the time.

The agency stated that there have been crashes in Laguna Beach (California), Norwalk (Connecticut), Cloverdale (Indiana); West Bridgewater (Massachusetts); Cochise County Arizona; Charlotte, North Carolina; Montgomery County, Texas; Lansing; Michigan; and Miami.

The National Transportation Safety Board has also investigated some of Tesla’s crashes and recommended that Tesla and NHTSA limit Autopilot’s use in areas where it is safe to operate. NHTSA should also require Tesla to use a better system for monitoring drivers’ attention. NHTSA has yet to act on any of these recommendations.

NHTSA demanded that automakers report all crashes involving partially or fully automated driver assistance systems in June.

These measures indicate that the agency is taking a more aggressive stance than it did in the past on safety of automated vehicles. For fear of limiting the adoption of potentially life-saving technology, the agency has been reluctant about issuing regulations.

Tesla Inc. shares, which are based in Palo Alto (California), fell by 2% just before the opening bell.