Witnesses said the Tesla auto did not brake prior to impact, the police said in a statement, adding it was unknown if the autopilot feature in the Model S was engaged at the time. Police Sgt. Samuel Winkler said the car's air bags were activated and that the Tesla's 28-year-old driver suffered a broken right ankle, while the driver of the mechanic truck didn't require treatment.
Tesla's Autopilot system is a complex beast that uses radar, cameras with 360-degree visibility and sensors to detect nearby cars and objects. It's built so cars can automatically change lanes, steer, park and brake to help avoid collisions.
"In the wake of this violent impact, the lithium ion batteries could have provoked a process known as "thermal runaway", that is, a rapid and unstoppable increase in temperature", said Bellinzona police in a Facebook post on Monday.
Cantonal police in Ticino are not commenting on the fatal accident which is one of three incidents involving Tesla cars in recent days.
A Tesla Inc Model S crashed at speed into a truck from the city's Unified Fire Authority in South Jordan, Utah, late on Friday after failing to slow for a red light, South Jordan police said on Monday.
"What is truly surprising about this accident is the fact that the Model S had an accident with a speed of 60 miles per hour, and the driver only broke his ankle".
The National Transportation Safety Board has not opened an investigation into the crash, spokesman Keith Holloway said, though it could decide to do so. Last week, the independent federal agency opened a probe into a Model S that caught fire after crashing into a wall In Florida.
Two 18-year-olds were trapped in the vehicle and killed in the flames.
The NTSB and the National Highway Traffic Safety Administration are also looking into the performance of the company's Autopilot system in the March crash of a Tesla Model X on a California highway.
Additionally, the NTSB is also looking into a 2016 accident in which the driver of a Tesla slammed into a tractor trailer and died.
Musk said "the probability of an accident with autopilot is just less", and he insisted the vehicle had functioned exactly as it was created to in the California crash.
In his email to staff, Musk said Tesla was "flattening the management structure to improve communication", combining functions and trimming activities "not vital to the success of our mission" in the reorganisation.
In March, an Arizona pedestrian was killed by a self-driving Uber vehicle, in the first death of its kind.
"As a reminder for drivers of semi-autonomous vehicles, it is the driver's responsibility to stay alert, drive safely, and be in control of the vehicle at all times", Winkler added. Waymo, Alphabet's self-driving unit, said on Sunday that Matthew Schwall had joined from Tesla, where he was its main technical contact with U.S. safety investigators.