COLUMBUS, Ohio -- An ex-deep-sea treasure hunter is violating his plea agreement by giving evasive answers about the fate of 500 missing gold coins pulled from an historic shipwreck, say a group of investors who helped fund the hunt for the ship.

Defendant Tommy Thompson went missing three years ago amid demands he appear in court. He and his longtime female companion were apprehended in January at a hotel where he was living near Boca Raton, Florida.

Thompson has faced accusations of cheating investors since he discovered the S.S. America, known as the Ship of Gold, in 1988. The gold-rush-era ship sank in a hurricane off South Carolina in 1857 with thousands of pounds of gold aboard, contributing to an economic panic.

The 161 investors who paid Thompson $12.7 million to find the ship never saw any proceeds. Two sued -- a now-deceased investment firm president and the company that once published The Columbus Dispatch newspaper.

Thompson pleaded guilty in April to contempt of court for failing to appear before a federal judge in 2012. Part of his plea deal requires him to answer questions in closed-door sessions about the whereabouts of the gold.

The first of those hearings was Oct. 19. A federal prosecutor chastised Thompson afterward, calling his answers evasive and concerning, and scheduled another hearing for Oct. 26.

But Thompson's former attorney canceled the hearing two days beforehand, saying he told Thompson not to answer further questions at the risk of incriminating himself. That attorney, Steve Nolder, no longer represents Thompson, and declined to comment. A message was left with Thompson's new attorney.

Thompson faces two years in prison and a maximum fine of $250,000 at his Nov. 24 sentencing.