We move to a break in the mystery surrounding a lottery jackpot, almost three years after the winning numbers were drawn. A new person has come forward that may help investigators unravel this... See More
We move to a break in the mystery surrounding a lottery jackpot, almost three years after the winning numbers were drawn. A new person has come forward that may help investigators unravel this mystery. Abc's linsey davis has that story for us. Reporter: This morning, iowa prosecutors may be about to hit pay dirt when it comes to solving the mystery of a $16.5 million lottery jackpot, that nearly three years later, has gone unpaid. The breakthrough came after investigators offered immunity to a canadian man, in exchange for information about just who bought this winning ticket in a des moines gas station back in 2010. Someone has the ticket. The iowa lottery wants to give away the money. Reporter: For an entire year, lottery officials only new one thing for sure. Someone had won. They just didn't know who. And then, just before the deadline, new york attorney crawford shaw came forward. We have the winning ticket. Reporter: Shaw was claiming the prize on behalf of an anonymous trust. Stunningly, just days later, he backed out. And the prize was forfeited, baffling officials. The question is, what the hell is going on here? Reporter: Lotto officials scoured security video, looking for clues, anything about who really bought the winning ticket. But the mystery remained unsolved, leading law enforcement to open a criminal investigation. It appears to me, on the face of it, the criminal acts have been committed, with respect to people claiming to be the rightful owner, who haven't. And it attempted fraud. Reporter: As you can imagine, a lot of people have come forward, alleging the winning ticket was stolen from them. Based on the rules, it's to late for a payout. But lotto officials says this serves as an important reminder for people to sign their lottery ticket so there's no question as to whom the ticket belongs. If I had signed mine, we wouldn't be in this mess now. And you wouldn't be here right now.
This transcript has been automatically generated and may not be 100% accurate.