Two vehicles reportedly engaged in self-drive modes - a Tesla Model S and a General Motors Chevy Bolt - have been involved in separate road accidents in California.
Culver City's fire service said the Tesla had "ploughed into the rear" of one of its fire engines parked at the scene of an accident on Monday.
The car's owner subsequently claimed it had been in Autopilot mode at the time.
The GM incident resulted in a collision with a motorbike in San Francisco.
The rider says the car - which was using GM's Cruise Automation technology - caused him serious injury and is now suing GM, according to local newspaper The Mercury News.
GM has alleged the motorcyclist was at fault. The event dates back to December, but has come to light only now.
Car-makers suggest self-drive technologies should make the roads safer, but at present California requires a driver to remain behind the wheel so they can retake control at short notice.
However, the state's Department of Motor Vehicles is currently considering new regulations that would allow tests on public roads without a human sitting in the driver's seat.
The US National Transportation Board (NTSB) has said it will investigate the Tesla crash.
According to a tweet by the Culver City Firefighters, the Model S was travelling at 65mph (105km/h) when the impact occurred.
"Amazingly, there were no injuries," an official said.
Tesla has the ability to analyse data gathered by its vehicles' on-board computers to determine the cause of crashes, and has shared information with the press about previous high-profile accidents.
However, for now the car company has limited itself to saying that "Autopilot is intended for use only with a fully attentive driver" and that it has instructed drivers to keep their hands on the steering wheel while employing it.