A Tesla car crashed into a tree and burst into flames in Houston, Texas, killing two people.
Officials said the car, which has a driver-assist system called Autopilot, appeared to have been driving itself at the time of the crash, according to media reports.
"Our preliminary investigation is determining – but it is not complete yet – that there was no one at the wheel of that vehicle ... we are almost 99.9 per cent sure," Harris County Precinct 4 constable Mark Herman told the Wall Street Journal.
One of the victims was in the front passenger seat and the other was in the back seat of the Tesla 2019 Model S when it veered off a bend at high speed, according to the newspaper.
It took emergency responders and firefighters about four hours and about 120,000 litres of water to put out the fire, said Mr Herman.
The high-voltage batteries used in Tesla cars made things difficult for rescue workers.
The batteries are known to reignite several times after firefighters extinguish a fire involving electric vehicles, according to the US government's National Transportation Safety Board.
“If a high-voltage battery is damaged, energy remains inside any undamaged cells, with no path to discharge it ... responders have no way of measuring how much remains ... and no way of draining, other than time-consuming methods as allowing a battery fire to burn itself out,” said the NTSB.
Tesla did not immediately respond to The National’s request for comment. After the crash, the electric car maker’s founder and chief executive Elon Musk tweeted about the safety of Tesla’s driver-assist system.
“Tesla with Autopilot engaged now approaching 10 times lower chance of accident than average vehicle,” he said on Sunday.
All new Tesla cars come with the standard driver-assist feature but the company clearly said that it does not plan to make its vehicle fully autonomous.
“While these features are designed to become more capable over time, the currently enabled features do not make the vehicle autonomous.”
Autopilot is supposed to be engaged where there is a “fully attentive driver” who has his “hands on the wheel and is prepared to take over at any moment”, the California-based company said.
In the first quarter of this year, Tesla registered one accident for every 6.74 million kilometres driven with Autopilot engaged.
The company recorded one accident for every 3.29 million km when Autopilot was not engaged but other active safety measures were switched on.
Last month, the National Highway Traffic Safety Administration said it opened 27 investigations into crashes involving Tesla vehicles.
The US road safety agency sent its team to investigate two crashes in Michigan and Detroit. The Michigan accident happened on March 17 when a Tesla in Autopilot mode crashed into a parked police car.
The Detroit accident was on March 11 and involved a Tesla that crashed into a lorry, leaving a passenger in serious condition.
In December 2019, a speeding Tesla Model S slammed into a Honda Civic at an intersection in Los Angeles, killing two people.