Tesla said Thursday a driver was killed while using the "autopilot" self-driving mechanism on its Model S electric car, leading to a federal safety investigation.

Tesla said the National Highway Traffic Safety Administration (NHTSA) had opened a "preliminary evaluation" into the performance of Autopilot after the electric car company notified the agency of the fatality.

In a statement, Tesla said it the fatality was "a tragic loss" and was the first such incident with autopilot activated.

"This is the first known fatality in just over 130 million miles (209 million kilometers) where Autopilot was activated," the company said.

"Among all vehicles in the US, there is a fatality every 94 million miles. Worldwide, there is a fatality approximately every 60 million miles," it said.

"It is important to emphasize that the NHTSA action is simply a preliminary evaluation to determine whether the system worked according to expectations."