The United States mistakenly granted citizenship to at least 858 people who were previously ordered to be deported or removed from the country, according to a Department of Homeland Security audit released Monday.

The Department of Homeland Security inspector general said immigrants were able to apply for citizenship using different names or birthdates because government databases failed to retain records of their fingerprints, the Associated Press reported.

Inspector General John Roth said all of the immigrants wrongly granted citizenship are either from "special interest countries" that pose national security risks to the U.S. or neighboring countries that have high rates of immigration fraud.

A DHS official said the records are incomplete because the agency consistently used paper fingerprint cards up until 2010 that were never uploaded to federal databases, and therefore cannot be electronically searched. DHS said immigration officials are now digitizing those files and vowed to review every file identified as potentially fraudulent.

The fingerprints for up to 315,000 immigrants who are fugitive criminals or were given final deportation orders are missing from federal databases. The report said Immigration and Customs Enforcement has not reviewed nearly half of those cases to add fingerprints to federal databases.

"This situation created opportunities for individuals to gain the rights and privileges of U.S. citizenship through fraud," Inspector General John Roth said. "To prevent fraud and ensure thorough review of naturalization applications, [U.S. Citizenship and Immigration Services] needs access to these fingerprint records."

At least three of the immigrants wrongly granted citizenship subsequently acquired aviation or transportation work credentials, which allows them to access secure areas in airports or maritime facilities, according to the AP. Their credentials have since been revoked, Roth said. A fourth person identified now works as a law enforcement officer.