Justice Department attorneys are preparing to file several complaints against unauthorized immigrants who obtained U.S. citizenship after being ordered for removal, a process that has stalled for months while the agency has been forced to address lawsuits challenging the Trump administration's immigration crackdown.

The Department of Homeland Security's inspector general revealed last September that more than 1,000 immigrants residing in the U.S. were erroneously granted citizenship after applying with different names or birthdates. The stunning error was partly due to the government's failure to maintain updated fingerprint records.

President Trump blasted the revelation at the time, telling supporters at a campaign rally last fall, "we made them citizens and they were getting ready for deportation."

"Can't have it," Trump said.

Only three individuals, however, who were recommended to the Justice Department for denaturalization proceedings have since been stripped of their citizenship status. And all three cases were litigated during the final months of Barack Obama's presidency.

"There are literally zero resources available to file affirmative litigation right now," a source close to the Justice Department told the Washington Examiner. "They're too busy with litigation coming in from folks challenging different initiatives."

The Justice Department has received nine referrals for civil denaturalization proceedings from U.S. Citizenship and Immigration Services since Trump took office — seven of which were received between July and August, according to a department spokesperson.

"Zero have been filed to date," the spokesperson said, adding that the top law enforcement agency takes "this issue very seriously and will continue reviewing such referrals to ensure that the rule of law is enforced."

An onerous process, revoking one's citizenship requires that the government prove an individual fraudulently procured their citizenship status or deliberately deceived federal officials during the naturalization process. Cases meeting one or both of those requirements are subsequently referred to the Justice Department for civil or criminal proceedings.

Federal officials rarely faced more than two dozen revocation cases annually until 1997, when the Clinton administration sought to denaturalize nearly 5,000 immigrants who had wrongly obtained U.S. citizenship during the former president's first term. Processing each revocation could take anywhere between a couple days to months, a Justice Department spokeswoman had said at the time.

Following its internal audit last September, DHS ordered a team to review every "case of possible fraud and where digital fingerprint records were not available at the time of the naturalization adjudication."

Of the 1,929 cases reviewed, approximately 1,600 "are being considered for referral for denaturalization proceedings," DHS spokeswoman Gillian Christensen said. Such referrals are then reviewed by government lawyers and filed in federal court by a local U.S. attorney or the Justice Department's Office of Immigration Litigation (OIL).

Identifying individuals with criminal records has been a priority for the review team as they are the likeliest to pose a threat to national security and need to be denaturalized and deported more quickly, Christensen said.

"Every case is so individual, so not only are we identifying cases but also then prioritizing which ones we should go through first," she noted.

A former top DOJ official slammed the administration for failing to move more quickly to identify and denaturalize criminal illegal immigrants who improperly procured citizenship. The official described that task as OIL's "highest priority" in the waning months of the Obama administration.

"If there have been nine referrals so far and none have been filed, that, in my view, is unacceptable," the official said, adding that delays in adjudication "incentivize this type of behavior."

"Either it's been deprioritized consciously or unconsciously because there have been so many cases filed around the country challenging the travel ban, diversity visas, funding restrictions for sanctuary cities, and the use of immigration enforcement," the source continued. "Once you start publicizing that [Justice Department officials] aren't prioritizing this, it will only get worse."

One DOJ official said the agency could hire more hands now that the Trump administration's hiring freeze has been lifted, even though the Office of Immigration Litigation had previously been exempt from the order.

David Martin, who served as general counsel of the now-defunct U.S. Immigration and Naturalization Service during the Clinton years, said without additional resources it could take "many, many months or even more than a year to see these cases through from start to finish."