Researchers are working to identify the remains found in 10 wooden coffins.
Drone footage shows a mass grave in New York City with dozens of coffins.
The Oklahoma Archeological Survey conducted a geophysical survey of areas of soil in October.
The militants executed at least 700 members of the Sheitat tribe in these villages after the group refused to pledge loyalty
The historic city fell under the militants' control last year.
Tens of thousands have died and more than 2 million displaced in the ongoing conflict.