Gustavo Salazar, Gabriel Salazar and Andres Rendon allegedly filed hundreds of false tax returns, according to the U.S. Attorney’s Office for the Northern District of Georgia. Prosecutors say the returns claimed false tax withholdings and other information to generate refunds, which were sent to post office boxes the men controlled.

The defendants and other alleged co-conspirators received more than 16,000 refund checks, prosecutors said. The checks were allegedly cashed at a north Georgia check-cashing business, with the proceeds paid out in bulk cash and laundered.

All three men are charged with conspiracy to commit mail and wire fraud, mail fraud and conspiracy to commit concealment money laundering. Gustavo and Gabriel Salazar also face charges of making false statements on immigration forms. Authorities said the men are Mexican nationals and are not U.S. citizens. The allegations have not been proven in court.

IRS Criminal Investigation agents conducted a court-authorized search at a BP gas station on West Fayetteville Road in College Park, near Hartsfield-Jackson Atlanta International Airport. Agents blocked the entrances and were seen carrying boxes and containers from the business. Investigators also searched a home in Senoia, where two of the men were arrested; another arrest was made in Fayetteville.

The investigation involved IRS Criminal Investigation, Homeland Security, the U.S. Postal Inspection Service and the Bureau of Alcohol, Tobacco, Firearms and Explosives. The gas station’s owner said afterward that he was surprised by the operation and did not know what investigators were seeking.