CHICAGO (CBS) — The Cook County Forest Preserve District has abandoned plans for a new section of walking and biking path in Oak Forest, after crews dug up unmarked graves on the site of the old Oak Forest Hospital.

WBBM Newsradio’s Bernie Tafoya reports the county said the bones which were dug up will be reburied where they were found, and the area will be returned to a natural state.

Forest Preserve General Supt. Arnold Randall said crews working on plans for a new stretch of biking and walking trails dug up unmarked graves on the site of the old Oak Forest Hospital at 159th and Cicero. The district acquired the land as part of a plan for the Oak Forest Heritage Preserve, a combination of recreational trails, natural areas, a museum, recreations of a historic poor farm and 17th century Native American dwellings, and preservations of the historic cemetery.

Randall said contractors digging a trench next to an existing road that cuts through the property unearthed unmarked graves and human remains on Oct. 30.

The Oak Forest property had been the site of a poor farm and a tuberculosis sanitarium, and later a hospital. The property had also been used for the burial of poor people and unidentified people in unmarked graves between 1911 and 1971 in Cook County. Some 90,000 to 100,000 people were buried there during those 60 years.

Randall said the largest cemetery and some smaller satellite cemetery sites were indicated on a 1916 map the county has, but where the bones were found was not mapped.

“We encountered a location that was not mapped as a cemetery, and there was actually an existing road on the site already,” he said.

Because of the find, Randall said the county is working with the Illinois Historic Preservation Agency, and an archeologist, to properly reinter the remains where they were found.

“We’re basically going to remove any roads from that area … where it won’t be disturbed, it will be a sort of natural area,” he said.

The Oak Forest Heritage Preserve has been scheduled to open next spring.