A 48-year-German driver died when his car hit the barrier in the central reservation of a motorway in the southern Swiss canton of Ticino, turned over and burst into flames.
"The violent impact of lithium-ion batteries could probably have caused a phenomenon called 'thermal runaway', i.e. a rapid and unstoppable increase in temperature," Ticino fire brigade said on its Facebook page.
Lithium-ion batteries can, under exceptional circumstances, have a sudden and unstoppable increase in temperature, in a sort of chain reaction that leads to the complete destruction of the batteries and the car, said fire safety expert Guido Zaccarelli in an article quoted by the firefighters.
A Tesla spokesman said: "We are deeply saddened by this accident, and we are working to establish the facts of the incident and offer our full cooperation to local authorities."
On Friday a Tesla Model S crashed at speed into a truck in South Jordan, Utah. Police said the driver told them she had been using Autopilot at the time and was looking at her phone. The U.S. National Highway Traffic Safety Administration (NHTSA) is also reviewing a Florida crash of a Tesla last week that killed two teenagers. Autopilot is not believed to be a factor in that crash, but the NTSB is looking into the cause of the intense fire triggered by the crash.
On a related note, The Wall Street Journal today reported that Tesla had looked into and rejected technology such as eye-tracking to ensure that Tesla owners weren't misusing Autopilot.
"It came down to cost, and Elon was confident we wouldn't need it," a source told the WSJ.
However, Elon Musk responded to the report in a tweet, saying that eye-tracking was rejected as ineffective. It is, however, used by some other manufacturers such as Cadillac in its Super Cruise system.
Recently, a driver in England lost his license for activating Autopilot then moving into the passenger seat.
Reporting by John Revill