The Islamic State’s genocide on Iraq’s Yazidi community continues as security forces discovered two mass graves filled with bodies near Mosul on Sunday. Kurdish Peshmerga forces found the graves, which had at least 18 people buried in them, along with identification cards in the Shababit junction area in northwestern Iraq, according to reports. Officials said Islamic State members apparently used a bulldozer to cover the graves with sand.

Mahma Xelil, the mayor of Sinjar, said the two latest Yazidi grave sites accounted for the 28th and 29th Yazidis mass graves discovered by security forces since the Islamic State took over the Sinjar area in 2014, Reuters reported. Xelil said the grave site total would most likely add up to more than 40 as Kurdish forces continue to push Islamic State militants further out of Mosul and the surrounding areas.

The Yazidis accounted for about 400,000 people, however, since the Islamic State invaded Sinjar, thousands of people have been captured, enslaved and killed, leading the United Nations to rule the Islamic State’s attack on Yazidis a genocide. In March, the Obama administration also formally called the Islamic State’s attack on Yazidis and other religious groups in Iraq a genocide.

The Yazidis, whose religious beliefs combine aspects of Islam, Zoroastrianism and Christianity, is just one of the many groups facing wipe-outs by Sunni extremists. Shiite Muslims and Christian populations surrounding Mosul have also faced the Islamic State’s brutality.

Although the Islamic State has lost about a third of the territories occupied in Iraq and Syria, in part due to U.S.-backed airstrikes against jihadist militants, some 3,500 people, mostly women and children, are believed to still be in captivity in various areas under the Islamic State’s control, the Office of Kidnapped Affairs in Duhok said in a statement. Eighteen captives reportedly escaped from Tal Afar in northern Iraq after Shiite forces regained control following invasions in areas south and west of the town.