Kevin McCoy

USA TODAY

Five suspects have been arrested for involvement in a growing IRS impersonation scam that has bilked an estimated $36.5 million from 6,400 victims nationwide, federal officials said Tuesday.

Nabbed Monday in Miami, Fla., the suspects are accused of making multiple calls in which they claimed to be IRS or Treasury officials, told unwitting victims they owed tax debts, and threatened arrests if payments weren't sent immediately, the office of the Treasury Inspector General for Tax Administration said.

The five allegedly persuaded the victims to wire payments via MoneyGram, Walmart2Walmart and other money wiring services.

"These arrests indicate that TIGTA is making significant progress in our investigation of the IRS impersonation scam that continues to sweep the country, resulting in reported taxpayer losses of more than $36 million," Treasury Inspector General J. Russell George said in a statement.

IRS scam calls and threats heat up this summer

The arrests stemmed in part from an Oct. 2015 call to a fraud hotline established by the Senate Special Committee on Aging, TIGTA said. The caller reported that her husband, after receiving a purported IRS arrest threat and demand for a nearly $2,000 payment, drove to a local Walmart store to wire the money.

The distraught victim crashed his car while en route, but was so worried that he left the accident scene to wire the money, said Sen. Susan Collins, R-Maine, who chairs the Senate panel.

The fraud hotline investigator who received the victim’s report traced the wire transfer to Minnesota, and provided the information to TIGTA. Investigators identified two of the suspects by checking Walmart surveillance tapes, Collins said.

Cautioning taxpayers to avoid being duped, George stressed that legitimate IRS and Treasury officials would not make phone demands for tax payments via money transfer systems.

George's office identified the suspects as Jennifer Valerino Nunez; Dennis Delgado Caballero; Arnoldo Perez Mirabal; Yaritza Espinosa Diaz and Roberto Fontanella Caballero. The five are allegedly responsible for almost $2 million in fraud schemes that victimized more than 1,500 victims, TIGTA said.

The suspects are Cuban nationals who were known to each other and resided in the Miami area, TIGTA said. Investigators believe they may have used electronic equipment that enabled them to mask their calling locations as they phoned victims in Minnesota, Arkansas and Texas.

Federal court complaints filed in the three states were not immediately available Tuesday.

The investigation is continuing as TIGTA searches for other suspected conspirators and copycats who may have tried to duplicate the alleged crime scheme. Since mid-April, some scammers have instructed victims to pay purported IRS tax debts with Apple iTunes cards, TIGTA said.

Follow USA TODAY reporter Kevin McCoy on Twitter: @kmccoynyc