The inspector general found that the immigrants used false names or birthdates to apply for citizenship with USCIS and such discrepancies weren't caught because their fingerprints were missing from government databases.
The report states fingerprints are missing from federal databases for as many as 315,000 immigrants with final deportation orders or who are fugitive criminals. ICE has not reviewed about 148,000 of those immigrants' files to add fingerprints to the digital record.
According to the Associated Press, "The gap was created because older, paper records were never added to fingerprint databases created by both the now-defunct Immigration and Naturalization Service and the FBI in the 1990s. ICE, the DHS agency responsible for finding and deporting immigrants living in the country illegally, didn't consistently add digital fingerprint records of immigrants whom agents encountered until 2010."