Kurdish Syrian Democratic Forces (SDF) said that they had arrested 125 suspected ISIS members during an anti-ISIS security operation in a northeast Syria camp for relatives of militants.

The sprawling tent camp houses 62,000 people.

The U.S.-backed SDF has been sweeping the al-Hol camp in northeastern Syria and is trying to clear the area’s biggest displacement camp of ISIS operatives and recruiters. ISIS terrorists have murdered more than 40 people, execution-style, in al-Hol since the beginning of the year.

SDF officials told the Voice of America that the first phase of the operation has been completed. SDF troops, numbering over 5,000, conducted a tent-by-tent search for Islamic State operatives resulting in the arrests which included 20 sleeper cell leaders responsible for the murders taking place inside the camp. 

While the SDF claim to have made significant progress, they also say that the danger is far from over. The al-Hol camp holds mostly Iraqis and Syrians, but also people from several other countries.

Ali al-Hassan, a spokesman for the Asayish internal security forces, said in a statement that “Many members of the IS terrorist organization have moved to the camps as civilians in order to reorganize the camp and create a conducive atmosphere.”

“Without international support, it will not last long,” he said of the sweep. “The international community must help, and the citizens of every country must return to their homeland,” he added.

The SDF was aided by Kurdish Asayish security forces. Heavily armed troops surrounded the camp while others began the search and, using biometric data, were able to identify and arrest the Islamic State operatives. They also confiscated mobile phones and laptops. One Kurdish SDF official told AFP that the ISIS operatives dug trenches inside the camp to hide the electronic devices.