The University of South Florida-led team recovered bones, teeth and numerous artifacts in each of the 55 graves found at the shuttered Arthur G. Dozier School for Boys, said project leader Erin Kimmerle, a USF associate professor.
Researchers also recovered a brass plate in one grave that read, "At Rest," likely from a coffin lid, she said.
The team of more than 50 people from nine agencies excavated the cemetery on the 1,400-acre campus in Marianna, 60 miles northwest of Tallahassee, between September and December.
Some graves, believed by researchers to be from the late 1920s to the early 1950s, were found under roads or overgrown trees, well away from the white, metal crosses marking the 31 officially recorded plots.
The state closed the 111-year-old school it ran in June 2011 after a century of scandal involving allegations of abuse, beatings, rapes, torture and even murder of students by staff.
Despite a string of state and federal investigations over the years, school officials repeatedly denied wrongdoing.
The Florida Department of Law Enforcement concluded in January 2010 there had been no foul play, the Tampa Tribune reported. State Attorney Glenn Hess said two months later no criminal charges would be filed.
"Locating 55 burials is a significant finding, which opens up a whole new set of questions for our team," she said.
The team will now try to identify the remains, determine the causes of death and return the remains to relatives for proper burials.
"We're hoping to bring the families resolution and hopefully some sense of peace," Kimmerle said.
Researchers will start searching next week for additional unmarked graves on the school grounds. As they did earlier, they will look for signs of burial shafts using ground-penetrating radar, she said.
They will also use specially trained K9 teams to locate graves, Kimmerle said.
Funding for the 2-year-old effort comes from the state Legislature and the U.S. Justice Department's National Institute of Justice.