A federal judge in Ohio has ordered a former deep-sea treasure hunter to explain why he shouldn't face new penalties for failing to answer questions about 500 missing gold coins.

Judge Algenon Marbley scheduled a hearing after Tommy Thompson said in a Monday court hearing he wasn't going to answer questions about the coins as required by a plea deal.

The 63-year-old Thompson faces two years in prison on a criminal contempt charge for failing to appear before a judge three years ago to answer similar questions. A message was left with Thompson's attorney.

Marbley could keep Thompson behind bars until he answers questions about the coins, which were found in 1988 aboard a sunken 19th-century ship.