Looting Indigenous burial mounds is serious. That's why a suspicious sighting has become a big deal.

A recent call for volunteers to help care for ancient Indigenous burial mounds in northwest Wisconsin may also have attracted some suspicious visitors.

Now, state and Indigenous officials are seeking more information, and reinforcing the legal and cultural severity of the issue.

The Barron County Sheriff’s Department received a call on June 26 that two suspicious men were spotted walking at a group of Indigenous mounds carrying a metal detector and a pickaxe. The caller said the men told him they were not with the county nor an Indigenous mound preservation group.

The incident occurred shortly after an article published in a local newspaper described the efforts of archeologists and conservationists to form a group of volunteers to help preserve the mounds. The site is known as the Pleasant Plain Mound Group, which contains 25 visible conical mounds that may have been built around 500 B.C.

“I am incredibly saddened to hear about the possibility of looting (at the site),” said Amy L. Rosebrough, Wisconsin State Archeologist with the state’s Historic Preservation Office. She said most Wisconsin residents know that the remaining ancient Indigenous mounds are protected by state law, making it illegal to dig, desecrate or disturb the ground within burial sites of any age or type, including mounds.

“Mound systems like Pleasant Plain have been badly treated over the years, and most have been destroyed,” Rosebrough said. “The law protecting burial sites was put in place to help places just like this.”

She said she hopes that the men encountered on the property left without doing harm. “Should evidence of disturbance or desecration be found we are required by statute to forward this matter to the appropriate authorities,” Rosebrough said.

Barron County Sheriff Chris Fitzgerald said police did not find anyone on the site when they arrived and did not find anything disturbed.

Archeologist Kurt Sampson, who organizes mound preservation volunteers and runs Effigy Mounds Initiative, said area authorities need to track the potential looters down based on the license plate information that was provided to them.

“I still firmly believe the more educated people are about the importance and prehistoric and historic significance of the mounds around the state the better off they are,” he said. “Unfortunately, there are always going to be a few bad apples out there that will disregard the law, but this is actually a very rare thing.”

Any person who intentionally digs up a cataloged burial site in Wisconsin faces up to a $10,000 fine and anyone who benefits financially from the excavation faces up to a year in prison.

Sampson said anyone seeing a disturbance of any kind on a mound site should call 911 and contact Rosebrough at the Wisconsin Historic Preservation Office at 608-264-6496.

Frank Vaisvilas is a former Report for America corps member who covers Native American issues in Wisconsin based at the Milwaukee Journal Sentinel. Contact him at fvaisvilas@gannett.com or 815-260-2262. Follow him on Twitter at @vaisvilas_frank.