TAMPA — The ongoing investigation into a burial ground at Florida's oldest reform school has turned up possible buckshot in the remains of a boy who died in state custody.

University of South Florida researchers disclosed the find to aides of the Florida Cabinet earlier this week in an update of their excavations at the cemetery at Dozier School for Boys in Marianna. The pellet-shaped artifact was found near what would have been the boy's stomach.

Hillsborough County sheriff's Detective Greg Thomas sent the small metal object to the Florida Department of Law Enforcement for analysis. FDLE ballistics experts found that the "lead ball cannot be definitively determined to be an ammunition component due to damage and corrosion; however, it is consistent with 000 Buck size shot pellets for various muzzle loading balls based on weight, size, and physical appearance."

Stories have swirled for decades about foul play at the brutal school, open from 1900 to 2011. In 2012, USF anthropologists began investigating a small burial ground surrounded by pine trees on a forgotten corner of campus, where pipe crosses marked what was said to be the final resting place for 31 boys who died at the school. Using ground penetrating radar and excavation techniques, they found 55 graves, many in the woods outside the marked cemetery. Remains were found buried under trees and brush and under an old road.

USF's new 15-page report, an update for the Florida Cabinet, says researchers also found buried among the remains a cache of syringes and drug bottles dated 1985, a modern water cooler containing the remains of a dog and "various kinds of garbage."

The possible projectile was found among the remains of a 14- to 17-year-old boy, most likely of African-American ancestry. They know he was buried clothed and in a casket, but can't determine when he was put into the ground. The burial location suggests he died during the later part of the period that the Boot Hill cemetery was in use. The last recorded burial at the school was 1952.

At a news conference Thursday, forensic anthropologist Erin Kimmerle, who is leading the research, said the remains were so deteriorated that she couldn't tell what killed the boy. But Thomas said it was possible a projectile the size of the lead ball they found could cause a fatal injury.

USF has also identified two more sets of remains: Sam Morgan, using DNA, and Bennett Evans, presumptively identified based on age, burial location and context. That brings the number of individuals identified to five. Evans was an employee of the school while the others were inmates.

Although researchers found 55 graves, they believe they've unearthed the remains of 51 individuals. That's because three sets of charred remains were found mixed up in seven different graves. They believe these remains belonged to victims of a 1914 dormitory fire that killed seven to 10 people, most of them boys who had been locked in "dark cells" on the third floor and were unable to escape when the building ignited.

They don't know where the other fire victims were buried, but think their remains could be with the debris of the burned dormitory, which was dozed under.

Excluding the fire victims, USF has found the remains of 48 children. But they have the names of only 43 boys from school records. Among those 43, nine were white and 34 — nearly 80 percent — were documented as "colored." The youngest burial was 6-year-old George Grissam who had been paroled for labor and was brought back to the school in 1918, unconscious.

The report also says researchers talked to former wards from the early 1960s who claim to have been sexually abused by guards and can name their perpetrators, who may still be alive. If the victims were younger than 12, there's no statute of limitations on rape. Researchers encouraged police to get involved and said they "found the testimonies used in our research to be honest and credible."

"We hope that it's not just glossed over or pushed aside," Kimmerle said.

The research team will continue field work at the shuttered school until August. They plan to excavate the burned dormitory structure to try to locate the missing remains. They also intend to open a discussion about what to do with the remains they've found and how to properly rebury and memorialize them.

Contact Ben Montgomery at bmontgomery@tampabay.com or (727) 893-8650.