The fire ignited Saturday at about 10:15 p.m. just behind the cockpit of an ABX Air Boeing 767 cargo airplane.
Fire crews extinguished the blaze and two flight crewmembers, who were preparing to start the engines when the fire ignited, escaped without injury. The fire caused "substantial damage to the aircraft."
Five NTSB investigators joined representatives of the FBI; Bureau of Alcohol, Tobacco, Firearms and Explosives; Transportation Security Administration; San Francisco Fire Department and Airport Rescue and Fire Fighting to look into the incident.
The NTSB reported today that within a week prior to the fire, the cargo carrier received a threat against an unspecified aircraft. The preliminary investigation has not revealed any indication of an explosive or incendiary device.
The nature of the threat made against the cargo airline was not immediately released.
The 21-year-old airplane was originally configured for passenger operations before Israel Aerospace Industries modified it in 2004 into a cargo plane.
The Israel Ministry of Transport has chosen a representative to join in the investigation and Israel Aerospace Industries will serve as a technical adviser to the representative.
Both members of the flight crew were interviewed Tuesday and NTSB investigators expect to complete to on-scene phase of the investigation by Sunday.
ABX Air is a cargo airline that operates out of Wilmington, Ohio, and has 15 hubs throughout the country, according to the company's Web site.
