According to NBC News, reports indicate that hundreds of migrants have entered the United States through a network linked to ISIS, with the locations of over 50 individuals currently unknown. The Department of Homeland Security (DHS) has flagged more than 400 foreign nationals from Central Asian countries and other regions as “subjects of concern” due to their arrival through this ISIS-affiliated human smuggling network. While U.S. authorities have detained over 150 of these migrants, Immigration and Customs Enforcement (ICE) is unable to locate more than 50 of them.

“The fact that the whereabouts were unknown is clearly alarming,” former FBI counterterrorism section chief Christopher O’Leary told NBC News.

He mentioned that ICE may be conducting these arrests to eliminate any possible threat to national security that individuals may present, even in the absence of concrete evidence of a planned attack on the United States. “I believe the [U.S.] is scrambling to locate these individuals, and using the immigration charges is not uncommon,” O’Leary stated. “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.”

According to NBC News, a number of migrants who were apprehended have already been deported from the country. The remaining migrants have been located in 17 different states within the United States and may soon face arrest by authorities. While some of the detained or repatriated migrants have faced charges related to immigration violations, none of them have been accused of any terrorism-related offenses thus far, as reported by NBC News. This information comes in the wake of a nationwide sting operation conducted by the FBI and DHS earlier this month, resulting in the apprehension of several foreign nationals suspected of having ties to terrorism. Notably, these individuals were also citizens of Tajikistan, a Central Asian country.

“Over the last few days, ICE agents arrested several non-citizens pursuant to immigration authorities,” a joint statement from the FBI and DHS about the operation reads. “The actions were carried out in close coordination with the FBI’s Joint Terrorism Task Forces.”

“The individuals arrested are detained in ICE custody pending removal proceedings,” the statement continued. “As the FBI and DHS have recently described in public and partner bulletins, the U.S. has been in a heightened threat environment.”

The escalated tensions surrounding a possible terrorist attack arise amidst a significant surge in the influx of suspected terrorists at U.S. borders during the Biden administration.