The U.S. inspector general has criticized the Homeland Security Department (search) for not having the tools necessary for border patrol to identify wanted criminals once they're detained.

The U.S. Border Patrol (search) does not have the ability to run fingerprints from illegal aliens through a single database and get a full immigration and criminal history. The agency's I-DENT (search) system and the FBI's I-AFIS (search) system aren't integrated and won't be for another four years — two years later than anticipated.

While there's no way of knowing exactly how many aliens are detained and released without any check of their criminal records, U.S. officials say the number of dangerous felons who are caught then released back across the border is large.

Customs and Border Protection Commissioner Robert Bonner (search) said it's still a goal to integrate the fingerprint databases, but in the meantime, two checks have to be done with two sets of fingerprints — which means less efficiency and the possibility of letting more criminals loose.

Critics say the ongoing lack of a comprehensive background check system makes Americans more vulnerable.

"This should be the highest priority there is because these people who are criminal aliens who re-enter this country … really are terrorists," said Gene Davis, a retired border patrol deputy chief. "They come in and they rob and they rape and they murder and they kill."

Click here for a report by Fox News' Dan Springer.