Syria’s Kurds have released 30 Syrians suspected of affiliation to the Islamic State group after guarantees from tribal leaders, a spokesman said Tuesday, adding more should be freed soon.

The Kurdish-led Syrian Democratic Forces (SDF) hold thousands of suspected IS fighters after years of leading the U.S.-backed fight in the country against the jihadi group.

The suspects are mostly Syrian and Iraqi — Iraq was the other key crucible of the conflict with IS — but they also include hundreds of foreigners.

A spokesman for the Kurdish authorities in northeastern Syria said tribal leaders had requested that 300 Syrian detainees be freed, and that 30 were approved and released on Sunday.

“Those being released have no blood on their hands and have not been proven guilty of any crime,” the Kurdish region’s foreign affairs spokesman Kamal Akef told AFP.

They might have joined the extremist group to earn a living or because they were forced to, he said.

They “are being released with guarantees from the tribal leaders,” the official added, without specifying what guarantees are involved.

“In the coming days, some more will be released in waves” to return to the provinces of Deir Ezzor and Raqqa in the east and north of Syria, he said.

Backed by airstrikes by a U.S.-led coalition, the SDF in March last year expelled IS from their last patch of territory in eastern Syria.

Earlier that month, nearly 300 Syrian men were freed after tribal chiefs lobbied for their release, including in Raqqa, the Kurdish authorities said.

At the time, the Syrian Observatory for Human Rights, a Britain-based war monitor, said it was not the first release of IS-linked prisoners, but the number was particularly large.

The Kurds have also said they were releasing hundreds of suspected IS-linked women and children from overcrowded camps for the displaced.