The U.S. government has mistakenly granted citizenship to more than 800 immigrants that it was supposed to have deported.
An internal Homeland Security Department audit released Monday found the 858 immigrants came from countries that pose a national security risk to the United States or countries with high rates of immigration fraud. The report did not identify the countries.
The Homeland Security Department's Inspector General John Roth said the immigrants used different names or birth dates to apply for citizenship. He said the mistakes happened because the applicants’ fingerprints were missing from government databases.
"This situation created opportunities for individuals to gain the rights and privileges of U.S. citizenship through fraud," Roth said.
At least three of those who were mistakenly granted citizenship were able to use their citizenship to get jobs in security-sensitive fields, including work at commercial airports and maritime facilities. The Department of Homeland Security say all three have had their security credentials revoked.
A fourth person has become a law enforcement officer.
Investigators last year identified another 953 cases that also appear suspicious.
The Department of Homeland Security says the report highlights what has long been a challenge for immigration officials — the fact that old paper-based records containing fingerprints cannot be searched electronically.
The audit recommends that paper fingerprints be digitized and added to the government's database. It also recommends that officials create a system to evaluate the hundreds of people who were mistakenly approved for citizenship.
Charges have been brought in two of the cases.
Immigrants are required to disclose any previous aliases they have used with immigration officials as well as their immigration history, but they sometimes omit that information.
Republican presidential candidate Donald Trump has made the vetting of immigrants a central part of his platform. He has called for a temporary ban on immigration from countries "compromised by terrorism" until a stronger vetting process can be put in place.