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.