Limavady scam: Tens of thousands stolen from bank accounts
Up to 30 people in Limavady, County Londonderry, have lost tens of thousands of pounds in "serious and sophisticated" banking fraud in the past two months.
Detectives have said a gang has used telephone and computer scams to divert money from bank accounts.
In many cases, hoax callers claim they are from banks or other financial institutions.
The BBC understands that one man has lost his life savings of up to £60,000.
"People have lost everything they ever had," said Sergeant Ian Hunt, who is helping with the investigation.
"This is very worrying for the town. There are cases around the province but Limavady is a particular concern at the moment.
"We are not sure why Limavady is a key target. Maybe it's because we have lost a few banks recently and jobs.
"The themes of the approaches vary, but they are generally aimed at getting people to disclose personal financial details such as PIN codes.
"A typical ploy is to claim that a suspicious transaction had been identified in a person's bank account and that often leads on to persuading the individual to transfer money from a genuine account into another account, which, of course, the fraudster controls.
"What we are saying is, if you get a call or email, do not give out financial details or agree to any transaction, and do not respond to email addresses or phone numbers provided by the caller.
"You can always check the legitimacy of any approach by contacting the named bank on a number you know to be genuine.
"It has been known for fraudsters to keep the telephone line open after their conversation, so that when you make a call, you are talking to them again. Avoid this by first of all making a call to a family member or friend so that you can be sure the line is clear.
"Many banks also offer a 24-hour customer services telephone services. You should take the number from official bank statements."
Danske Bank have sent letters and emails to their customers, warning them about the scams.