Twenty-seven potential graves identified earlier this year at the infamous Dozier School for Boys in north Florida have turned up no evidence of human remains, state authorities and University of South Florida researchers investigating the site said Tuesday.

The Dozier School, a Marianna reformatory where hundreds of children were beaten and abused for decades, had long been rumored by survivors to hold more than the 55 burials researchers in past years had identified on Dozier’s campus. Workers this spring had stumbled upon the more than two-dozen possible “clandestine” graves not far from the school’s official burial grounds, prompting the Department of State to announce it would investigate the anomalies and order a full survey of the school’s site for the first time.

But researchers dispatched to the school’s campus this month to investigate the possible graves — removing the top layer of soil, using ground penetrating radar and excavating by hand — found that the anomalies were “mostly evidence of tree roots from a previously removed pine tree forest,” according to the announcement.

“While the recently reported anomalies were found using remote sensing technology above the ground, we were able to look below the surface and clearly determine no graves or human remains are present,” Erin Kimmerle, the forensic anthropologist leading the research team, said in a statement. “Studying this area of the property was an important step for us to be able to answer the questions that had been raised.”

The Florida State Reform School, as Dozier was first known when it opened in 1900, has become notorious for the regular assaults and beatings that many young boys sent there have recounted in years since. Meant to be a site for young offenders to be rehabilitated, detainees were regularly whipped and assaulted by guards. Some were sent to a small cinder-block building they named the White House, where they were beaten with dozens of lashes from a leather and metal strap, some so viciously their skin would split.

Corporal punishment was banned in the 60s, but beatings and abuse at Dozier continued for years. By the time Dozier was finally shuttered in 2011, the U.S. Department of Justice had reported “systemic, egregious and dangerous practices exacerbated by a lack of accountability and controls” at the site, along with little staff training or treatment for detainees with substance abuse or mental health issues.

Researchers, led by Kimmerle, identified nearly five dozen sets of burials hidden at Dozier in the years since. Survivors, decades after leaving the campus, have also spoken up about Dozier’s history: Named the White House Boys for the building that became synonymous with their abuse, many have called for years for a complete search of Dozier’s campus for more possible graves.

With the 27 anomalies investigated, researchers are proceeding with surveying the entire 1,200-acre campus for the first time to see if any more sites needed to be further investigated. That campus-wide search will use existing radar-like laser mapping data — built with LIDAR (Light Detection and Ranging), which utilizes lasers rather than radio waves the way radar does — to identify aberrations.

The LIDAR approach will allow researchers to pinpoint any additional sites that should be searched further, likely using ground excavation and other field techniques that researchers have used previously. That process may take until the end of the year.