President Obama's push to curb deportations through executive action has opened the door for thousands of illegal immigrants to collect Social Security benefits, both lawfully and by exploiting weaknesses in the agency's ability to detect fraud.

Justice Department officials in Arizona, South Carolina and Florida declined to prosecute illegal immigrants after the Social Security Administration proved they were using the Social Security numbers of dead Americans to secure benefits, an agency inspector general report revealed.

While Cosme Lopez, a spokesman for the U.S. Attorney's office in Arizona, declined to discuss the specifics of why his office rejected the case, he told the Washington Examiner there are several reasons why prosecutors would refuse to press charges.

"When we, and our agency partners, decide whether to pursue prosecution in any particular case, we must consider a number of factors, including the Department of Justice's priorities, our limited resources and, when relevant, whether the underlying conduct resulted in any economic loss," Lopez said.

Investigators with the Social Security Administration's inspector general said they had confirmed the illegal immigrants in question stole identities from dead people to work.

Nancy Wicker, spokesperson for the South Carolina attorney's office, said a major consideration in her office's decision to prosecute an undocumented immigrant using a stolen Social Security number is whether the Department of Homeland Security plans to deport that person.

"We would also consider whether the individual used the identity of the dead person to commit fraud or other offense, or whether he used it only to secure employment," Wicker told the Examiner. "Since the latter circumstance is not likely to involve a victim or economic loss, we may be less inclined to devote resources to such a prosecution."

She noted some Social Security crimes do indeed incur losses, and that her office "vigorously prosecutes" fraud cases that involve a victim.

Many illegal immigrants who have been allowed to remain in the country thanks to Obama's controversial executive orders could be collecting Social Security payments by using dead Americans' identities.

Between 2006 and 2011, the Social Security Administration suspended payments made under 66,920 Social Security numbers after finding that the names and numbers didn't match its records, the agency's inspector general found.

Dozens of individuals' W-2 tax forms had been filed using the same Social Security number in some cases.

In one instance, a single Social Security number had spawned 613 claims, the report said.

The Social Security Administration lost billions of taxpayer dollars by making payments to people that were at least 112 years old and presumed dead, the Examiner reported.

But the Obama administration's recent immigration moves have positioned thousands more illegals to reap the government benefits without resorting to fraud.

In a letter to Social Security Administration commissioner Carolyn Colvin Thursday, Sens. Jeff Sessions, R-Ala., and Ben Sasse, R-Neb., demanded to know how many Social Security numbers the agency had granted illegal immigrants as a result of the president's executive action.

The letter noted the agency had handed out 90,000 numbers to illegals who received work authorization after Obama signed a January 2013 order deferring deportation for immigrants unlawfully brought to this country as children.

Sessions and Sasse pressed the commissioner on whether the Social Security Administration had paid illegal immigrants disability or supplemental income benefits.

Obama's latest executive actions sparing nearly 5 million illegal immigrants from removal granted those same individuals access to Social Security, according to a congressional memo obtained by the Examiner.

Signed in November of last year, the White House's orders defer deportation for the parents of U.S. citizens, young illegals and permanent residents.

"For the purposes of Social Security, as defined in regulations, foreign nationals in deferred action status are considered lawfully present," the memo said.

Illegal immigrants need only a temporary work visa to obtain a Social Security number and begin amassing credit in the program.

Those individuals can even claim credit for work they performed before the government authorized them to do so by presenting minimal evidence of their prior wages, though the memo noted "it is unclear how easy it will be for a foreign national to prove that earnings credited to a Social Security number that was not issued to the foreign national (i.e., credits earned while the person was working without authorization) belong on his or her earnings record."

"If the individual had work authorization at some point, all of his or her Social Security-covered earnings would count toward insured status," the memo said.

In other words, undocumented immigrants can now rack up Social Security credit both before they obtain authorization to work in this country and after that temporary authorization expires.

What's more, the Social Security Administration has been aware of the strain illegals place on the agency for years.

"Social Security Administration acknowledged unauthorized noncitizens' intentional misuse of Social Security numbers has been a major contributor" to the growth of cases in which benefits are suspended due to discrepancies, an August 2013 inspector general report said.

"Social Security Administration staff told us employers hired unauthorized workers because nothing prevented them from doing so," the report said, noting employers knew they would face no consequences from the agency and that they "were not concerned about potential IRS sanctions."