CNN in New York —. The National Highway Traffic Safety Administration has started an investigation into the safety of Tesla’s Full Self-Driving feature, known as FSD, following at least one deadly accident involving a pedestrian. The investigation is focused on four incidents involving vehicles that were using the FSD feature. In one incident, a pedestrian was hit and killed, according to the agency. In another incident, there was an injury. In both accidents, the Tesla vehicle utilizing FSD “was involved in a crash after entering a zone with limited road visibility.” The agency’s statement regarding the initiation of the investigation mentioned issues like sun glare, fog, or dust in the air. FSD plays a crucial role in Tesla’s strategies for future expansion and profitability. The feature, available as an $8,000 add-on, necessitates that drivers remain in the driver’s seat and be prepared to take control of the car to prevent accidents. Tesla and CEO Elon Musk assert that the feature is already safer than driving by humans. The company has shared plans for fully autonomous cars that will not include steering wheels, accelerators, or brake pedals. Last week, Musk announced a plan for a fleet of self-driving “robotaxis” as well as a service enabling Tesla owners to rent out their vehicles for ridesharing to earn money when they are not using them. Although Musk has claimed that these offerings would allow Tesla to become the most valuable company globally, investors largely found the presentation underwhelming, resulting in a nearly 9% drop in Tesla’s shares the day following the evening event. This isn’t the first occurrence of the NHTSA stating that it is looking into Tesla’s self-driving capabilities.