Three-time NASCAR champion Tony Stewart has been cleared by a grand jury investigating a dirt-track incident in upstate New York in August that killed a young driver, a county prosecutor said Wednesday.

Stewart, one of the biggest names in auto racing, struck and killed Kevin Ward Jr., 20, during a non-NASCAR sprint car race Aug. 9 on a dimly lit part of the Canandaigua Motorsports Park track, which is about an hour's drive west of Syracuse.

Ontario County District Attorney Michael Tantillo said authorities submitted possible charges of manslaughter in the second degree and criminally negligent homicide against Stewart and the grand jury "determined that there is no basis to charge Tony Stewart with any crimes."

Stewart's representatives couldn't be reached for immediate comment.

Stewart, who had often driven in non-NASCAR races, skipped the next three NASCAR races following the incident.