What was the most probable cause of the air crash?

A small US plane carrying a half ton of marijuana burnt after crashing in Sinaloa, Mexico, on Sunday. Federal judicial police sources in Sinaloa reported that the plane went down close to a clandestine airstrip located on a farm about 30 kilometers north of Galiancan, capital of Sinaloa. Mechanical failure is believed to have caused the crash. The pilot was killed and much of the drug was destroyed in the fire.