Forrest County Coroner Butch Benedict said the remains, found Tuesday on the grounds of Camp Shelby, were in an Army uniform. Firearms were nearby. The 136,000-acre base is just south of Hattiesburg.
Lt. Col. Doril Sanders, a base spokesman, would confirm only that human remains were found on the base. He said the Army's crime lab will use DNA and dental records for identification.
Pfc. Ryan K. Longnecker, who was 19 at the time, was training at Camp Shelby when he disappeared Aug. 6, 2007, along with his military-issued 9mm pistol and M4 assault rifle.
Shirley Ann Longnecker, the soldier's paternal grandmother, told The Associated Press on Wednesday that military investigators found her grandson's identification with the remains. However, she said the military stopped short of saying the remains belonged to Ryan Longnecker.
She said she doesn't know what may have happened to him.
"He seemed to be a people person, but he wasn't getting along with some of the people down there," Shirley Ann Longnecker said, adding that her grandson had once tried to get out of the military.
Longnecker is currently the only soldier reported missing from Camp Shelby, Sanders said. However, neither Sanders nor Benedict could confirm if the remains belong to the missing soldier.
Benedict said "the condition of the bones would probably be consistent" with decomposition that would occur in the timeframe since Longnecker was last seen.
The remains were found between two roads and "probably a few hundred yards from a building in a secluded area," Benedict said.
After Longnecker disappeared in 2007, the military led the investigation for months, then said Longnecker was absent without ordered leave and turned the case over to the U.S. Marshals Service.
Longnecker was supposed to deploy with the Kentucky National Guard's Battery B, 2nd Battalion, 138th Field Artillery unit when he disappeared. About 160 members of Longnecker's unit and hundreds of troops from other areas were training at Camp Shelby at the time.
"He was outgoing, independent and stubborn. A little bit on the wild side, but he finished everything he was supposed to in the Army," Shirley Ann Longnecker said. "He seemed very excited about going the last time I saw him."
Col. Phil Miller, a spokesman for the Kentucky National Guard, said Wednesday that Kentucky officials are aware that remains were found but are waiting for the investigation to "provide further information to us."
Camp Shelby, which has hundreds of acres of forests and expansive training grounds, was federally mobilized in 2004 to train Guard soldiers for missions overseas. More than 50,000 National Guard troops from Alaska to Puerto Rico have passed through the facility since then.