The US government has launched a formal investigation into Tesla’s Autopilot driving system over concerns it has difficulties identifying parked emergency vehicles.

Almost every car Tesla has sold in the US since the start of the 2014 model years will be affected by the probe – an expected 765,000 vehicles.

The US National Highway Traffic Safety Administration announced the investigation on Monday, which covers the Models Y, X, S, and 3 from the 2014 through 2021 model years.

According to the announcement, the agency has identified 11 crashes since 2018 in which Teslas on Autopilot have hit vehicles at scenes with flashing lights, flares, an illuminated arrow board or cones warning of hazards.

The NHTSA says that 17 people were injured and one killed as a result of these crashes.

There have been a number of car crashes associated with drivers using Tesla’s autopilot feature when not paying attention to the road – some of which are being investigated by the National Transportation Safety Board in the US.

In one incident, an Apple engineer died when his Tesla Model X on autopilot hit a concrete barrier – something he had previously complained to his wife about the autopilot feature veering him towards.

Earlier this year a motorist in the San Francisco Bay Area who was spotted in the back seat of his Tesla as it travelled down a freeway was arrested for reckless driving.

Police were alerted after receiving a number of calls describing a person seated in the backseat of a Tesla Model 3 without anyone in the driver’s seat while travelling on Interstate 80 across the San Francisco-Oakland Bay Bridge.

Tesla vehicles can be “easily tricked” into driving in autopilot mode with no one at the wheel, according to testers from a major US consumer organisation just days after a Tesla crashed in Texas, killing the two men in the car.

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The NHTSA said it has sent investigators to 31 crashes involving partially automated driver assist systems since June of 2016.

These systems can keep a vehicle centred in its lane and a safe distance from vehicles in front of it, with Tesla’s Autopilot setting enabling the car “steer, accelerate and brake automatically within its lane” as long as a driver remains behind the wheel to take over in any emergency situations.

Of the 31 total crashes investigated by the agency, 25 involved Tesla Autopilot, and 10 deaths were reported in connection with these incidents, according to data released by the agency.

“The investigation will assess the technologies and methods used to monitor, assist and enforce the driver’s engagement with the dynamic driving task during Autopilot operation,” NHTSA said in its investigation documents.

The agency will also examine how well Tesla’s system can detect objects and events, and where it is allowed to operate.

NHTSA says it will examine “contributing circumstances” to the crashes, as well as similar crashes, but the probe could ultimately lead to a recall or other enforcement action.

Shares in Tesla, which has disbanded its media office and as such was not reachable for comment, fell 2% before markets opened this morning.