SAN FRANCISCO -- FBI and Israeli officials are now involved in the investigation of a fire that damaged an ABX air cargo plane at San Francisco International Airport after it was revealed that the airline received a threat against an unspecified aircraft less than a week before the blaze.

KTVU Channel 2 has learned that federal investigators will be at SFO through the weekend to examine the cargo plane that caught on fire. The plane remains in a restricted area with a black tarp covering the fire ravaged-portion of the aircraft. A mobile command center has been set up next to the plane.

On Thursday, the national transportation safety board posted the following statement on its website: "it was reported that within a week prior to the accident, the cargo carrier had received a threat against an unspecified aircraft. Preliminary examinations have not revealed any indication of an explosive or incendiary device."

No detail has been given about how the threat was made.

The fire ignited Saturday at about 10:15 p.m. just behind the cockpit of an ABX Air Boeing 767 cargo airplane.

ABX has a contract with DHL to transport cargo. Two flight crew members were getting ready to start the engine to take off from SFO to a sort facility at its company headquarters in Wilmington, Ohio.

The incident caused SFO authorities to evacuate three nearby buildings.

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 Wednesday 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.

On Friday night, airport officials said this incident has not caused any changes in security because SFO is always on high alert as an international airport.