After a Medford couple filed their state and federal income taxes in the spring of 2013, they discovered that someone had beaten them to the punch.

Someone using their Social Security numbers and birth dates had filed state and federal returns electronically earlier that spring, obtaining a federal refund wired to a prepaid debit card account in a Chicago suburb and a state refund wired directly to a bank account in Texas.

That set off a federal probe that uncovered a ring of Nigerian nationals in three states with ties to Vietnam who filed more than $48 million in bogus tax returns, with more than $12 million worth slipping past state and federal treasury officials before they were busted in 2015.

"There are in excess of 11,000 victims who have had fraudulent tax returns filed in their names in this case," U.S. Attorney spokesman Kevin Sonoff said.

The first two of the five defendants were sentenced Thursday in U.S. District Court in Medford.

Oluwatobi Reuben Dehinbo, 32, was sentenced to nine years in federal prison and ordered to pay $2.7 million in restitution. Oluwaseunara Temitope Osanyinbi, 36, was sentenced to six years in prison and ordered to pay $876,161 in restitution.

Both are Nigerian nationals who were living in the Atlanta area at the time of their arrests, and both face deportation following their sentences, Sonoff said.

"Those are some pretty righteous sentences, and there are still more to come in this case," said Ryan Thompson, a special agent with the Internal Revenue Service in Tacoma, Washington.

Michael Kazeem, 24, a Nigerian national who was living in Atlanta, pleaded guilty to mail fraud, conspiracy to commit mail fraud and three counts of aggravated identity theft, and is awaiting sentencing.

Emmanuel Kazeem of Bowie, Maryland, has a July 31 trial date, while a fifth defendant, Oluwamuyiwa Abolad Olawoye, 31, of Marietta, Georgia, has not offered a plea nor has a trial date set, federal court records show.

All remained lodged Friday in the Jackson County Jail. 

The Federal Trade Commission, which tracks identity theft, concludes that about 70 percent of all identity thefts are used for tax fraud, yet much fewer than 10 percent of the attempts make it through the IRS, Thompson said.

"We're doing a really good job of catching these, stopping the refunds and prosecuting," Thompson said.

In this case, search warrants in Illinois, Maryland and Georgia turned up numerous email and instant-messenger accounts used by the defendants and other alleged co-conspirators connecting the defendants to an identity-theft scheme run out of Lagos, Nigeria, since at least 2011, according to the DOJ.

The group was in possession of personal identification information of more than 250,000 people, including identities stolen from an Oregon database and sold to the Nigerians by sources in Vietnam, the DOJ states.

The group used the stolen information to file Personal Identification Numbers with the IRS, which allowed the members to bypass IRS authentication procedures, obtain pre-paid debit cards in the victims' names and set up accounts for direct deposits of the bogus returns, the DOJ states.

In 2014, at least 2,000 wire transfers totaling $2.1 million of money withdrawn from those debit cards was transferred to Nigeria, the DOJ states.

Osanyinbi came to the United States in 2013 on a student visa and quickly began filing fake tax returns and even paid a woman $4,500 to marry him so he could get permanent-resident status, the DOJ states.

Dehinbo came to the U.S. in 2012 and started filing false returns a year later, and the DOJ states he even tutored others on how to work their fraud.

Before coming to the U.S., Dehinbo was involved in finding hackers to gain stolen credit-card information, gave credit-card information and PINs to others and engaged in online romance scams by posing as a Swedish woman working for UNICEF in Nigeria, the DOJ states.

— Reach Mail Tribune reporter Mark Freeman at 541-776-4470 or mfreeman@mailtfribune.com. Follow him on Twitter at www.twitter.com/MTwriterFreeman.