The probe by the National Highway Traffic Safety Administration may become a setback for the growing number of tech and car companies investing heavily in autonomous driving technology. Regulators scrambled last year to write new rules for self-driving cars after Tesla announced hasty plans to release its limited Autopilot feature. But by then, the company had already sent ripples through the auto industry. In January, at the Consumer Electronics Show -- more or less the Detroit Auto Show of tech -- it seemed nearly every major car company unveiled some kind of autonomous feature. The first death in a self-driving car could stoke fears over the technology and temper the industry's growth. The majority of traffic accidents, which result in about 35,000 deaths in the U.S. every year, are caused by human error.