The National Highway Traffic Safety Administration (NHT) has launched a probe into about 75,300 model-year 2006 Nissan Frontier pickup trucks due to concerns about potential fuel leaks. The agency warns that the vehicles may pose an imminent fire hazard due to a strong, persistent odor of raw gasoline and sudden engine stalling during startup and operation. The probe was prompted by a petition alleging that the problems resemble those cited in previous recalls.