LEWISTON, Idaho — Students working on an extracurricular project to map grave sites at a cemetery in north-central Idaho discovered dozens of tombstones don't have remains buried beneath them.

Using ground-penetrating radar and Global Positioning System technology, the students eventually discovered unmarked human remains — including part of a foot bone — shallowly buried in a nearby city park that was once the original city cemetery.

The students believe that when the city of Lewiston decided a century ago to move most of the graves from the original city cemetery to the Normal Hill Cemetery so the grounds could be used for what is now Pioneer Park, workers or family members in some cases moved grave markers but not the remains beneath them.

"Of the 128 stones that we know were in Pioneer Park and are now in the Normal Hill Cemetery, we have checked many of them and we probably have 50 to 60 percent that have nothing underneath them," Steven Branting, the teacher who launched the "gifted-and-talented" student cemetery mapping project in 2001, said Thursday. "There may be well more than a hundred unmarked graves in the park."

The city of Lewiston passed an ordinance in 1893 declaring that unless family members relocated remains of loved ones from the original city cemetery, the city would have gravediggers do it and charge the family. But Branting said many families refused to exhume the graves or allow the city to relocate the remains, so only the markers may have been moved.

"It's fun to find out what really happened compared to what was said," said 16-year-old Chris Wagner, one of the students in the program. "People are kind of shocked to find out they put up a park where there was a cemetery."

Branting said their research shows the park's current playground area is in the center of what was once the original cemetery.

Branting developed the student project to investigate a 100-year-old rumor that a mass grave had been dug at the Normal Hill Cemetery to hold unidentified remains moved from the original city cemetery at Pioneer Park. The students used the noninvasive radar system to survey the Normal Hill cemetery and determined no such mass grave exists.

What they found was that many of the oldest grave markers at the Normal Hill Cemetery have no remains under them. That led students to conduct a radar survey of the park area, where they found at least two locations where unmarked human remains are buried.

"Things just kind of kept snowballing," said student Nate Ebel, 16.