The U.S. Immigration and Customs Enforcement (ICE) agency under former President Barack Obama may have failed to identify and arrest “highest risk” known or suspected terrorist aliens due to the absence of follow-up screenings after they are released.

Sanctuary cities that refused to cooperate with immigration authorities also prevented the agency from following up on the individuals in question, reveals a watchdog agency.

Based on a study of case files of detained aliens identified as known or suspected terrorists during fiscal years 2013 through 2015, the inspector general for the U.S. Department of Homeland Security (DHS) found:

ICE continues to face significant challenges with its screening of aliens who may have ties to terrorism. Auditors warn ICE may have missed opportunities to identify, apprehend, and adjudicate the status of aliens posing the highest risk to public safety and national security.

The audit indicated law enforcement agencies in sanctuary cities prevent ICE Enforcement and Removal Operations (ERO) from screening criminal aliens for terrorist ties.

“Some local law enforcement agencies will not honor ICE immigration detainer requests, which further hinders ERO’s ability to take criminal aliens into custody and apply KSTEP [the Known or Suspected Terrorist Encounter Protocol screening process],” explains the IG, adding:

Approximately 675 jurisdictions nationwide declined to honor more than 29,269 ICE immigration detainers from January 2014 through May 2017. When a state or local law enforcement agency declines to transfer custody of a removable criminal alien to ICE, the released alien may put the public and ERO personnel at risk and requires significantly more resources to bring the individual into ICE custody.

In September 2014, even former President Barack Obama’s DHS chief admitted that sanctuary cities that shelter illegals “hinder” the United States government’s ability to detect terrorists inside the United States.

John McCoy, the top DHS IG official who authored the audit, also found that most ICE offices charged with enforcement and removal operations did not have access to DHS “classified networks,” preventing them from exchanging sensitive information between U.S. agencies about known or suspected terrorists.

The IG suggested ICE may have released aliens with links to terrorism after it failed to properly vet them through the Known or Suspected Terrorist Encounter Protocol (KSTEP) screening process.

McCoy noted that his assessment stems from looking over 40 cases involving known or suspected terrorist aliens that suffered from “at least one instance” of screening process “noncompliance” at the hands of immigration agents during fiscal years 2013 thru 2015.

The findings prompted him to caution that noncompliance is “generating greater concerns regarding the population of aliens screened and determined to have no connections to terrorism.”

“ERO may [still] be missing opportunities to identify, take into custody, communicate status of, and make decisions on those [terror-linked] aliens who pose the highest risk to national security and public safety,” warns the inspector general.

Of the 40 cases, ICE reportedly failed to run all necessary electronic background checks to find out whether or not the alien is a known or suspected terrorist in about half of them (18).

In 10 of the cases, ICE “did not complete all requirements for documenting and reporting aliens confirmed as known or suspected terrorists,” reports the IG.

“Although the scope of our testing covered [fiscal years] 2013–15, ERO identified at least 19 more cases since January 2016 when field personnel did not transmit the required incident reports to ICE headquarters,” it added.

ICE cited “limited resources” and “human error” as a justification for not screening all aliens from terror-linked nations.

Currently, ICE can only apply the KSTEP vetting process to aliens under custody, notes the IG, adding that immigration agents are unable to find out if a migrant links up with terrorists after they are released into American communities.

ICE releases most aliens, notes the DHS auditor.

“As of June 2017, 33,701 aliens, or less than two percent of all aliens on ERO’s national docket, were in ICE’s custody and, therefore, subject to KSTEP screening,” reports the inspector general. “Although ICE screened these aliens at some point, ICE policy does not require periodic screening for connections to known or suspected terrorists.”

Terror-affiliated aliens hail from nations known as “specially designated countries” that “promote, produce, or protect terrorist organizations or their members,” reports the IG.

The IG explains that screening those aliens is intended to:

Determine whether those aliens were of interest to other Federal agencies based on any outstanding wants and warrants. However, because this policy only applied to aliens in ICE’s physical custody, or detained by ICE, OIG determined that ERO did not screen all aliens from specially designated countries, the large majority of whom were not in ICE custody.

As a result, the IG determined that ICE “faces challenges” in implementing the KSTEP screening process.

ICE is charged with immigration enforcement within the U.S. borders, dealing with both illegal and legal migrants who have broken the law.

The immigration agency, a component of DHS, acknowledges its shortcomings in identifying terrorism-linked aliens.

“ICE recognizes and is working to address the significant task and associated challenges with implementing the Known or Suspected Terrorist Encounter Protocol (KSTEP) screening process to identify aliens who may be known or suspected terrorists,” it wrote to the DHS IG.