BISMARCK, N.D. — A federal jury in North Dakota on Friday convicted a Rhode Island woman of helping scam elderly Americans out of millions of dollars, capping a large-scale Jamaican lottery scam case that authorities have been investigating and prosecuting for six years.

Jurors found Melinda Bulgin, 28, guilty of 15 counts of conspiracy, fraud and money laundering, after 3 1/2 hours of deliberations over two days. Defense attorney Kevin Chapman said he likely will appeal.

The Providence woman was the last of 27 defendants. The others all pleaded guilty or were convicted earlier in the scam that authorities say bilked at least 90 mostly elderly Americans out of more than $5.7 million. Authorities identified victims in at least five states: North Dakota, South Dakota, South Carolina, Texas and Arizona.

Authorities say scammers called victims about bogus lottery winnings, persuading them to send advance fees or so-called taxes to receive the purported winnings, then keeping the money without paying anything to the victims.

"When they (elderly) were vulnerable, Melinda Bulgin and these other co-conspirators preyed on them," Assistant U.S. Attorney Jonathan O'Konek told jurors.

The case is believed to be the first large-scale Jamaican lottery scam tried in U.S. courts. It began in September 2011, when then-82-year-old Edna Schmeets, of Harvey, North Dakota, was scammed out of about $400,000. During emotional testimony Thursday she described cleaning out her life savings, borrowing money from family and borrowing from the bank, so that she could continue sending checks.

"After that I was broke," she said.

Bulgin was accused of collecting money and funneling it between the U.S. and Jamaica via cheap flights she got through her job with an airline. She eventually was caught at a Jamaican airport in 2015 with nearly $15,000 she hadn't declared to customs officials.

That money came from Nancy Bauke, a 78-year-old widow in Tempe, Arizona, prosecutors said.

Bauke testified she was duped by the scammers even though she had worked as a financial adviser and taught financial planning classes. She said she sent a total of $25,000 to Bulgin and "did not receive one penny" in prize money.

Chapman told jurors that Bulgin's identity could have easily been used by other suspects in the scam, and that when she made admissions to authorities after her arrest in Jamaica she was "a young woman, scared, in a foreign country."

"We cannot trust the evidence in this case," he said.

The Federal Trade Commission estimates lottery scams could be a billion-dollar-a-year industry in Jamaica. The investigation into this scam began in 2012 and has involved the FBI, the U.S. Postal Inspection Service and the U.S. Justice Department.

"I'm happy for the victims, that we can bring some justice to them," Assistant U.S. Attorney Clare Hochhalter said outside the courtroom.