Victims are told they have won lottery
The police say they are aware of at least 10 cases of people in Northern Ireland falling victim to a lottery scam based in Canada.
The victims have been contacted by telephone or by letter by people claiming to be from lottery organisations.
They are told they have won a significant amount of money - usually around 120,000 to 130,000 Canadian dollars - but that cash advances are needed to pay government taxes before it can be released. No winnings exist.
One person from the province is believed to have lost £12,500 over a three-month period.
Police say that more people may have been duped by the fraudsters, but are too embarassed to come forward.
Detectives believe the scam originated in Canada and is being operated from there and they are working with authorities in the country.
Canadian police have set up a unit in Toronto to investigate the fraud.
Among the lottery names used are the Canadian Lottery, International Windfall and the New Australian Lottery.
PSNI Detective Chief Inspector Larry Cheshire said those behind the fraud can be quite convincing, but people should be immediately suspicious if they receive an approach of this kind out of the blue.
"If it does appear to be too good to be true it invariably is," Mr Cheshire said. "You get nothing for nothing in this life."
He urged anyone contacted with the lottery offer, or who has lost money to it, to contact the police.