Twenty-five Canadian suspects are charged with bilking American elders of $21 million as part of a “grandparent scam,” according to a federal indictment unsealed Tuesday.

All 25, said to have operated out of Montreal and resided there or elsewhere in the province of Quebec, were charged with wire fraud in a case alleging they were part of a tech-savvy operation that victimized hundreds of U.S. retirees, the U.S. attorney for Vermont said in a statement.

Thomas Demeo, special agent in charge of the Boston field office of the IRS Criminal Investigation Division, said the defendants were part of a “transnational criminal enterprise with the sole intent of defrauding hundreds of retirees of their life savings by preying on their emotions and deceiving them into thinking that their loved ones were in peril.”

Twenty-three of the 25 suspects were arrested in Canada on Tuesday, according to the statement. Two remain at large; the statement didn’t indicate where they are believed to be.