An offshore banking scam based in Grenada that cost thousands of U.S. and Canadian investors more than $170 million ended with federal prison sentences on Monday for four people. Douglas Ferguson, Laurent Barnabe, Robert Skirving and Rita Regale were officers of the First International Bank of Grenada, founded by former Portland mortgage banker and minister Gilbert Ziegler, who died in 2005 while awaiting trial. The investigation into the Ponzi scheme stretched over three continents and eight years, and involved expensive cars, a yacht, a multimillion-dollar home in Las Vegas, a palace in Uganda, claims of a 4-pound ruby and a shootout in Africa. The case was prosecuted in Oregon because almost $50 million raised during the scheme was funneled through a bank account in that state. Federal prosecutors said the Grenada bank offered interest rates as high as 300 percent and claimed to have earned more than $12 billion in high-yield trading, which turned out to be nothing more than phony documents with forged signatures. U.S. District Judge Garr King substantially reduced the government's sentence recommendation for Regale, 54, of Portland, citing her cooperation and ordering her to serve 18 months. Skirving, 59, of Portland, was sentenced to eight years and ordered to pay more than $32 million in restitution. Barnabe, 68, a Canadian citizen who lives in Lake Oswego, was sentenced to six years and ordered to forfeit his interest in money held in a foreign bank account. Ferguson, 74, of Portland, was sentenced to nearly four and a half years Regale, Ferguson and Barnabe must repay more than $26 million.