(CNN) The FBI lost track of dozens of foreign nationals it sponsored for entry into the United States to assist with investigations, the Justice Department's internal watchdog found.

The revelation stems from an audit by the DOJ Office of Inspector General into the department's use of immigration tools that allow law enforcement to sponsor non-US citizens to enter the country without requiring a traditional visa or residency.

This special category of immigration status is often used by the department to permit the entry of cooperating witnesses and confidential informants, who may be required to take part in investigative operations or trial testimony. Many of these individuals would ordinarily be unable to obtain traditional lawful immigration status due to their connections to criminal enterprises.

An agreement with the Department of Homeland Security -- the federal agency charged with conferring immigration status -- requires sponsoring law enforcement agencies assume full responsibility for tracking and monitoring the location and activities of foreign nationals they sponsor for entry.

In its review of the use of these special provisions by Justice Department component agencies, the inspector general found that the FBI was unable to account for at least 61 foreign nationals it sponsored. Furthermore, rather than proactively reporting the total number of those who disappeared, the bureau only notified DHS of 32 individuals no longer under the agency's control.

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