AL-HOL, Syria (AP) — The U.S. military said Wednesday it has started transferring detainees from the Islamic State group being held in northeastern Syria to secure facilities in Iraq.

The move came after Syrian government forces took control of a sprawling camp, housing thousands of mostly women and children, from the U.S.-backed Syrian Democratic Forces, or SDF, which withdrew as part of a ceasefire.

Troops on Monday seized a prison in the northeastern town of Shaddadeh, where some IS detainees escaped and many were recaptured, state media reported.

The Kurdish-led SDF still controls more than a dozen detention facilities holding around 9,000 IS members.

U.S. Central Command said the first transfer involved 150 IS members, who were taken from Syria’s northeastern province of Hassakeh to “secure locations” in Iraq. The statement said that up to to 7,000 detainees could be transferred to Iraqi-controlled facilities.