Military officials are trying to track down the origin of a 9-foot-long missile that a fisherman netted in the Gulf of Mexico and kept on his boat during a 30-hour trip back to shore, an Air Force spokesman said.

The AIM-9 Sidewinder missile, an air-to-air heat-seeking missile, may be debris from a military plane crash, or it may have been fired as part of a training exercise and missed its target, Air Force Master Sgt. Ken Hoffman said Monday.

The missile, which is 9 feet, 2 inches long and weighs 190 pounds when loaded with explosives, might also have been jettisoned by an aircraft with flying difficulties, he said.

The missile was detonated by a bomb disposal unit in Pinellas County at 8:30 p.m, Hoffman said, but it was not known whether the missile was inert or live.

The unidentified fisherman told police that he hauled the missile in with his net about 140 miles south of Apalachicola and put it on his boat to take it back to shore, Hoffman said.