JACKSON, Miss. (AP) — Workers building a road at the University of Mississippi Medical Center have found 66 unidentified graves.

Officials with the medical center say a construction crew found the unmarked human remains over a period from November through March. The graves were found 4 to 5 feet below the surface as workers dug down to lay a foundation for a roadbed.

The remains, in coffins, may have been patients of the former Mississippi Insane Asylum, which operated on the site from 1855 to 1935.

A team from Mississippi State University's anthropology department is removing and documenting the skeletons, aided by the University of Mississippi's Center for Archaeological Research and the state Department of Archives and History.

Nicholas Herrmann, a professor of anthropology and Middle Eastern culture at MSU, said he believes the graves are associated with the asylum, but a report from the state history agency says it may not be possible to pinpoint that.

MSU researchers will get two years to study the remains and try to answer that puzzle. Students are looking at the makeup of bones, trying to determine what the people ate and how old they are. Also enlisted are researchers at the University of Southern Mississippi, who will try to determine the age or type of coffin wood. That could give further clues about who's in the graves.

The remains were found in a wooded area near Lakeland Drive where UMMC is building a new access road.

"We might have built the roadbed on top of them if the subsoil had been solid," Ron Horne, director of construction projects at UMMC, said in a statement.

The coffins are about six feet long but narrow. "The weight of the soil compressed them," Herrmann said

After scholars finish examining the bones, UMMC plans to rebury the remains in an existing cemetery in the northeast corner of the medical complex. Already buried there are the remains of 44 people found in unmarked graves when the medical center dug out a steam line for a laundry in the early 1990s. Also transferred there were around 30 mostly marked graves. The medical center also buries the remains of anatomical donors in the cemetery.