Kurdish security officials told Reuters on Thursday that 15 of the prisoners had been recaptured.
They were being held at Fort Suse that is located just outside of Sulaimani city on the road to Dukan.
The whereabouts of the remaining six prisoners is unknown, the two officials told Reuters.
Reports of prison escapes in the Kurdistan Region are rare.
“Almost all of the convicted inmates who escaped are from Daesh,” said one Kurdish security source using another term for ISIS.
The office of the governor of Sulaimani was not immediately available for comment.
The number of ISIS prisoners held in the Kurdistan Region and Iraq is unknown.
Towards the end of major Iraqi offensives in 2017, there were many reports of ISIS fighters fleeing northward and being captured or killed by Kurdish security forces.
Update: 2:42 p.m.
