UPDATED 01/25/12 5:11 p.m.

BULL VALLEY, Ill. (CBS) – Two human skulls were found Tuesday in town of Bull Valley, near Crystal Lake, and authorities are trying to determine their source.

Bull Valley Police say the bones were discovered in the 1500 block of Cherry Valley Road in Bull Valley, a tiny town of about 700 people.

As CBS 2’s Mike Puccinelli reports, it was Tuesday morning and Leanne See-Garcia’s son was standing and waiting for his bus near the mailbox outside their home. That’s when he received the shock of his life.

“While he was waiting he noticed that there was a skull behind the mailbox,” See-Garcia said.

She said her son was concerned.

“He was excited, alarmed and a bit frightened because he’d just found what he thought was a human skull,” said See-Garcia.

McHenry County Sheriff’s police were also called to the scene, and investigators soon found another skull lying about 20 yards away from the first one.

Police searched the area for additional evidence Wednesday afternoon, but suspended that search in the late afternoon before dark. Meanwhile, the county Coroner’s office confirmed that both skulls were human, according to the Sheriff’s office.

Neither skull had any obvious signs of trauma. Both will be sent to Indianapolis where a forensic anthropologist will examine them

Despite the presence of more than 49 investigators, Bull Valley’s police chief was quick to reassure area residents.

“They have nothing to worry about whatsoever,” said Police Chief Richard Vance.

But the mystery of the two skulls was unlike anything long time residents of Bull Valley could remember.

“The big thing that happens here is a couple of raccoons crossing the road and today it’s a couple of skulls,” said area resident Robin Pendergrast.

See-Garcia said she believes the skulls likely ended up on her property after they were tossed from a moving vehicle.

Police said they don’t believe the skulls are linked to any missing person investigation from the area. They also couldn’t say if the skulls were from adults or whether they were male or female.

Police do not believe the skulls are connected with any open missing persons case.

They say there is “no danger to the community at this time.”