Suspects and Motives
No conclusive evidence was ever found, and the truth of the matter is that Hoffa’s death is still a mystery to this day. Yet, the authorities’ attention immediately turned to Mafia bosses Tony Jack and Anthony Tony Pro, the two who reportedly agreed to meet with Hoffa on the day of his disappearance. Sure, the suspects (the Mafia) and motives (money, power, you name it) were clear, the hard evidence proved far more mysterious.
Source: Mysterious Monsters
Officials even had to resort to hypnotizing suspects and witnesses to gather evidence against the Mob. It didn’t work though (surprise, surprise). The decades-old case opened a new chapter when the FBI began a new search in 2006 at a horse farm in Michigan.