A human jawbone found last month on the Iowa River in Marshall County belonged to a "prehistoric Native American," according to the Marshall County Sheriff's Office.

At about 4 p.m. Aug. 10, Marshall County Conservation Staff members and Marshall County Sheriff's Deputies found a lower human jawbone near the Iowa River during a biological survey.

Three other bones thought to be human were found in the area. An investigation was started to determine their origin.

"The jawbone was intact, but the condition was deteriorated indicating the jawbone was several years old," the release said. Marshall County Sheriff Joel Phillips said the bone was in "remarkable" condition when it was found.

"It's kind of a historic find," he said.

He said his office and the State Medical Examiner sent the remains to the Office of the State Archaeologist at the University of Iowa to conduct a further analysis.

"There is no medical comparisons because it was before medical records existed in the United States," he said. "We try to get things back to where they belong."

The archaeologist's office found that the mandible was likely from a middle age or older male "prehistoric Native American," according to a news release. Lara Noldner, bioarcheology director at the Office of the State Archeologist, said the office has not yet determined the exact age of the remains.

Following the office's analysis, Noldner said the remains will be reported to the federal government as a part of the Native American Graves Protection and Repatriation Act. The act, passed in 1990, aims to respectfully return remains and cultural items back to the Native American tribes from which they originated, according to the National Park Service.

Phillips said historically there were around 10 Native American camps along the river bank. Nodner said all the tribes will be notified of the remains so that they can returned for proper burial.

The remaining bones were not human, according to the Iowa State Medical Examiner's Office.