Investigators reportedly found no evidence of a defect in the fatal accident involving a Model S that failed to recognize a semi-trailer across the highway.

The National Highway Traffic Safety Administration has reportedly concluded its investigation into the first fatal Tesla Autopilot accident.

The agency opened an inquiry after a Model S slammed into the side of a semi-trailer on a Florida highway, shearing off the top of the sedan and killing its driver. Data logs showed that Autopilot was active at the time of the crash.

Tesla's internal review suggested the Model S' single front-facing camera failed to recognize the white trailer against a bright sky, while the radar system may have incorrectly interpreted the obstacle as an overpass bridge.

NHTSA investors asked for a copy of the data logs and extensive information regarding Autopilot's hardware sensors and software algorithms. The company was asked to outline the specific types of collision scenarios its automatic emergency braking (AEB) tech is designed to avoid, along with any known limitations.

After spending six months analyzing the information, the NHTSA has found no evidence of a defect, sources have told Reuters. Consequently, the agency is not expected to push for a recall.

Tesla warns drivers that they are required to keep their hands on the wheel and pay attention at all times. Facing criticism that some drivers may mistakenly believe the system is fully autonomous, the company later implemented additional protections to discourage drivers from misusing the technology. The latest Model S and Model X also come equipped with a much more advanced sensor suite, gaining multiple cameras and more radar sensors to produce a more accurate picture of the road and potential obstacles.