US-backed Syrian forces fighting the Islamic State group in Syria handed over more than 150 Iraqi members of the group to Iraq, the first batch of several to come, an Iraqi security official said Thursday.

The official said the IS militants were handed over to the Iraqi side late Wednesday, and that they were now in a “safe place” and being investigated.

The official, who spoke on condition of anonymity in line with regulations, said the Kurdish-led Syrian fighters, known as the Syrian Democratic Forces, are holding more than 20,000 Iraqis suspected of IS group membership in prisons in northern Syria.

The handover comes as the US-backed Syrian force is involved in a standoff over the final IS group-held sliver of land in southeastern Syria, close to the Iraqi border.

Dozens of people, many of them women and children, were evacuated Wednesday from the group’s tiny tent camp on the banks of the Euphrates River, signaling an imminent end to the territorial rule of the militants self-declared “caliphate” that once stretched across a third of both Syria and Iraq. More evacuations of civilians were expected on Thursday.

Some 300 IS group militants, along with hundreds of civilians believed to be mostly their families, have been under siege for more than a week in the tent camp in the village of Baghouz in eastern Syria.

It was not immediately clear whether the 150 Iraqis repatriated late Wednesday were among those recently evacuated from Baghouz or militants who had been captured earlier. The SDF is holding more than 1,000 foreign fighters in prisons that it runs in northern Syria, many of them Iraqis and Europeans.

The SDF, and more recently President Donald Trump, have called on countries to take back their nationals but few want them back.

Earlier this month, Iraqi Prime Minister Abdul-Mahdi said Iraq will take back all Iraqi IS militants in Syria, as well as thousands of their family members

Tuesday night’s handover marks the biggest repatriation of militants so far.

The Baghouz enclave’s recapture by US-backed Syrian fighters would spell the territorial defeat of IS group and allow Trump to begin withdrawing American troops from northern Syria, as he has pledged to do, opening a new chapter in Syria’s eight-year civil war.