ISIS made an unusual move by releasing 200 Yazidi prisoners in northern Iraq, according to a Kurdish military official statement on Sunday.

The Washington Post reports that the prisoners were held captive for five months and most of them are elderly and sick people. Three of them are young children.

The ISIS militants transported the prisoners from the northern town of Tal Afar and dropped them off at Khazer Bridge, near Irbil. The prisoners are in poor health and appear to have suffered abuse. They are now being given medical treatment in the town of Alton Kupri.

"Their situation is very bad, especially the psychological condition," said Hersh Hussein, a representative from the Irbil governor's office who was in Alton Kupri. "Regarding other diseases we provide first aid and the most important medical treatment."

The reason for the release appears to be that the prisoners were slowing down the militant group and that keeping them had become too much of a burden, according to a statement by Gen. Shirko Fatih, commander of Kurdish peshmerga forces in the northern Iraqi city of Kirkuk, to the Washington Post.

"It probably became too expensive to feed them and care for them," he said.

There have been previous reports that ISIS has forced its captives to convert to Islam. After the Sunni Muslim group attacked the town of Sinjar, near the Syrian border back in August, massacring hundreds of captive soldiers and tribal fighters, women were reportedly sexually abused, raped, and sold off. Some were taken as brides for the jihadists, while young boys were separated to train them to become jihadists.

There were an estimated 50,000 Yazidis who fled to the mountains on the day of the attack and still remain there.