More than 400 illegal aliens have entered the U.S. through an ISIS-affiliated human smuggling network under President Joe Biden, according to a report.

U.S. officials confirmed the Department of Homeland Security has identified these individuals. The report stated that 150 individuals have been arrested, but the whereabouts of more than 50 remain unknown as federal law enforcement officials work to locate and apprehend them. The remaining illegal aliens are spread across 17 states and are expected to be arrested soon.

The Biden administration claimed credit for tracking down the illegal aliens, citing “an abundance of caution.” The report indicated that the illegal aliens crossed the southern border amid the national security and immigration crisis exacerbated by Biden’s open borders policies.

The illegal aliens were released into the U.S. because there was no information at the time linking them to terrorism when U.S. Border Patrol contacted them. Countries where ISIS operates rarely have data connecting individuals to terrorism due to poor infrastructure and reluctance to share information with the U.S.

“The fact that the whereabouts were unknown is clearly alarming,” said former FBI counterterrorism section chief Christopher O’Leary. “I believe the [U.S.] is scrambling to locate these individuals, and using immigration charges is not uncommon. They are in violation of that law. And if you need to take somebody off the street, that’s a good approach to do it.”

This news follows the arrest of 8 ISIS terrorist suspects in U.S. cities earlier this month after they illegally crossed the southern border.