Police are probing what caused a fatal accident Sunday on I-95.The accident happened around 6 a.m. between exits four and five in Greenwich. Officials say a car driven by 23-year-old Reynaldo Sanchez, of Stamford, veered from the left lane and smashed into a Greenwich fire truck.Police say Sanchez was pronounced dead at the scene. One of his passengers, 26-year-old Jacqueline Bardales, was taken to Stamford Hospital, but did not survive. Another passenger, 24-year-old Gerson DeLeon, of Stamford, is in critical condition at Stamford Hospital.