The suspects were reportedly from Tajikistan and crossed into the United States from the southern border in 2023.
ABC News has learned the suspects were initially allowed to enter the U.S. after being vetted and no national security issues were uncovered.
But sources say in recent weeks, authorities uncovered information indicating ties or affiliation with ISIS-K.
Tajikistan has been described as a hotbed for recruiting for the terrorist organization.
And experts say the threat of terrorism has been rising.
"The threat level is the highest it's ever been, I think," said retired FBI agent Bobby Chacon. "We've heard that from both the attorney general and the FBI director in recent congressional testimony. It's keeping them up at night."
Agents with ICE carried out the arrests over the last few days.
Further details on the investigation were not immediately available.
Efforts are underway to deport the suspects. No terrorism charges have been filed.
The FBI and Department of Homeland Security released this statement:
"Over the last few days, ICE agents arrested several non-citizens pursuant to immigration authorities. 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. As the FBI and DHS have recently described in public and partner bulletins, the U.S. has been in a heightened threat environment. The FBI and DHS will continue working around the clock with our partners to identify, investigate, and disrupt potential threats to national security."