An audit released Monday finds that more than 800 individuals from countries of concern to national security or with high rates of immigration fraud were mistakenly granted citizenship.
Those individuals were from so-called "special interest" countries, which represent a U.S. security concern, or neighboring countries with a high rate of immigration fraud.
The individuals slipped through the system because their digital fingerprint records were not in the DHS or FBI's fingerprint databases, according to the inspector general report.
Citizenship and immigration officials identified that fingerprint records were missing for 315,000 immigrants who had been issued final deportation orders or who are criminals or fugitives. Officials have not yet reviewed about 148,000 of the records in an effort to digitize them, according to the DHS audit.
That leaves open the possibility of immigrants applying to become naturalized citizens being granted citizenship without officials having access to their full immigration and criminal history.
Government officials have been aware of the gap in records since at least 2008, when a Customs and Border Protection employee identified 206 cases where immigrants with final deportation orders obtained citizenship or other benefits using another name or other biographical information.
U.S. Citizenship and Immigration Services (USCIS) granted citizenship to at least 858 individuals who were ordered to be deported or removed under another identity, according to the Department of Homeland Security (DHS) inspector general report.