The Department of Homeland Security has identified 858 undocumented immigrants that were mistakenly granted U.S. citizenship, dating back to 2008.

U.S. Immigration and Customs Enforcement officials found an additional 315,000 with criminal records or final deportation orders did not have digital fingerprints on file, meaning they could apply without accurate background information available. USICS has yet to review about 148,000 of those cases.

"As naturalized citizens, these individuals retain many of the rights and privileges of U.S. citizenship, including serving in law enforcement, obtaining security clearance, and sponsoring other aliens' entry into the United States," read a DHS report released this month.

The problem came to light when a U.S. Customs and Border Protection employee found over 200 immigrants falsified person information - like name and date of birth - and subsequently received permanent residence. All came from "special interest" countries, or areas of national security concern, though the report does not specify which countries.

Of the 1,029 individuals identified, ICE has closed 90 investigations and opened over 30 more.

Fingerprint Failures

U.S. Citizenship and Immigration Services agents primarily use two criteria when interview applicants: fingerprints and immigration history. They look for aliases, criminal violations, deportation orders, and links to terrorism.

Next, they use IDENT, a DHS depository system used to digitize old fingerprint records. All the files weren't uploaded by 2008. Nor were they in the Federal Bureau of Investigation's similar Next Generation Identification system.

"The FBI repository is also missing records because, in the past, not all records taken during immigration encounters were forwarded to the FBI," the report read. As long as the older fingerprint records have not been digitized and included in the repositories, USCIS risks making naturalization decisions without complete information and, as a result, naturalizing individuals who may be ineligible for citizenship or who may be trying to obtain U.S. citizenship fraudulently."

One fingerprint card is supposed to be sent to the FBI while the other stays with the applicant's immigration file. According to investigators, these records were not always forward.

Individuals Slip Through

Investigators recommended establishing a plan for evaluating each of the new naturalized citizens who used multiple identities. The plan, they said, "should include a review of the facts in each case and, if the individuals is determined to be ineligible, a recommendation whether to seek denaturalization through criminal or civil proceedings."

The report cites a handful of unnamed immigrants who eventually attained security clearance, like "one U.S. citizen" who "is now a law enforcement official" and a transportation worker with "unescorted access to secure areas of maritime facilities and vessels."

At least two others received Aviation Workers' credentials.

Government agencies are working on implementing corrective action, which may include denaturalization. The Offices of the United States Attorneys accepted two cases but declined 26 others.

ICE, for their part, had identified 120 prosecutable individuals, some who carry Transportation Security Administration credentials.

"The fact that fingerprint records in these cases may have been incomplete at the time of the naturalization interview does not necessarily mean that the applicant was in fact granted naturalization, or that the applicant obtained naturalization fraudulently," DHS spokesperson Neema Hakim told CNN.

Hakim added, "Where the DHS review process finds that naturalization was obtained fraudulently, DHS will appropriately refer the case to the Department of Justice."