The remains were found on the ground late Friday on property northeast of Drexel in western Missouri after deputies working a theft case received information a tip, Cass County Sheriff's Cpl. Kevin Tieman said.
The deaths appeared to "drug-related" and were not "random acts," Tieman said. He said the remains did not appear to be related to any ongoing investigations.
The most recent remains were several months old, he said.
One man was arrested Friday and taken into custody on unrelated charges. He would not identify that man or say if he owned the property where the remains were discovered.
An anthropologist identified two separate sets of remains from the bone fragments, Tieman said, but authorities believed there were more.
"We are currently looking for six sets (of remains)," Tieman said.
The Kansas City Crime Lab and the Jackson County Medical Examiner were assisting.