After a six month investigation into the death of a Tesla driver following a fatal crash in July 2016, US auto safety regulators disclosed that they have found no evidence of defects in Tesla Motors.

Following the investigation of a Tesla Model S car which collided with a truck while using the semi-autonomous driving system in 2016, the US National Highway Traffic Safety Administration were unable to find any evidence that would have required  a safety recall of the Tesla vehicles.

The Tesla cars, which were released earlier than initially expected included new features such as built-in hardware that was expected to improve Autopilot’s features.

However, according to Reuters, US Transportation Secretary Anthony Foxx disclosed that one of the limitations found in Tesla’s autopilot is that the system was unable to detect the truck in the crash which resulted in the death of the driver.

TeslaFoxx explained that automotive makers have a duty to explain the limits that come with semi-autonomous systems.

Foxx said: “The auto industry is going to have to be clear about what the technology does and what it does not do, and communicate it clearly.”

In this case, the NHTSA found that the driver did not have any control of the car and was noticed to have set the car in cruise control at 74 mph, less than two minutes before the crash.

The agency said in a report that victim Brown “should have been able to take some action before the crash, like braking, steering or attempting to avoid the vehicle. He took none of those actions.”

The agency also asked Tesla to explain how it monitored its vehicle system and the steps it included before introducing the technology to prevent misuse.

Tesla responded: “The safety of our customers comes first, and we appreciate the thoroughness of NHTSA’s report and its conclusion.”

Musk also described the report as “very positive” in a tweet. The agency has announced that its decision to close the investigation is not based on the previous software improvements but the inability to disclose any defects from the crash.