IRBIL, Iraq - Kurdish forces said Sunday they uncovered two mass graves outside Sinjar, a northern Iraqi town near the Syrian border that was ruled by the Islamic State of Iraq and Syria (ISIS) for more than a year before the extremists were driven out last week.

The first grave uncovered was west of the town's center near the technical institute and contained 78 elderly women's bodies, the Sinjar director of intelligence, Qasim Samir, told The Associated Press. The second grave was uncovered about 15 kilometers west of Sinjar and contained between 50 and 60 bodies of men, women and children, he said.

More precise information from the second grave is unavailable at the moment, Samir explained, because the surrounding area is thought to be rigged with homemade bombs, preventing investigation teams from reaching it.

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ISIS captured Sinjar during its rampage across northern Iraq in the summer of 2014 and killed and captured thousands of members of the Yazidi religious minority, including women forced into sexual slavery. Kurdish forces backed by U.S.-led airstrikes pushed the extremist group out of the town in a two-day operation last week.

"These people (in the mass graves) were shot and buried during the Daesh invasion last year," Samir said, using an Arabic acronym for ISIS. Sinjar was taken by ISIS militants in August 2014 following the earlier fall of Mosul. During the same territorial push, ISIS advanced on Erbil, prompting the beginning of a US-led campaign of airstrikes against the group, first in Iraq and later in Syria.

A map shows the areas controlled by ISIS as of October 2015. The group's territory has shrunk considerably since then, but it remains entrenched in Raqqa, Syria, its de-facto capital, Iraq's 2nd largest city of Mosul, and other smaller cities and towns. CBS

A security official with the Kurdish militia forces known as peshmerga also confirmed the discovery of the mass graves.

"This is not a surprise," the official explained, requesting anonymity because he was not authorized to brief the media on the matter. "In other areas that have been taken back, we have found similar mass graves."

In the nearby town of Snuny, the Peshmerga uncovered 7 mass graves after retaking the territory earlier this year, the peshmerga official said.

Nawaf Ashur, a resident of Sinjar who was forced to flee with his family in August last year, said the news of the mass graves has jarred the Yazidi community.

"Everyone who was missing a family member was hoping that they were still out there, that they are still alive and maybe they'll come back," he said. Thousands of Yezidis remain unaccounted for more than a year after ISIS took a number of majority Yezidi towns in Iraq's north.

While hundreds of Yezidi women and girls have been released or escaped ISIS captivity, human rights groups estimate thousands still remain in ISIS custody.

"But now with the news of each grave found, we know not all of them will come back," he said. "Some of them are never coming back."