A Florida high school discovered that part of its campus sits atop a grave site containing approximately 145 graves.

King High School in Tampa, Florida is the site of the former Ridgewood Cemetery, which served as the burial ground for the city’s poor, many of whom were African American, from 1942 to 1959.

According to NBC News, the Hillsborough County Public Schools did an initial scan of the part of campus after it received it a tip from cemetery researcher and local historian Ray Reed about the land’s history.

Earlier this year Mr Reed also helped identify Zion Cemetery, another predominantly black cemetery, believed to contain some 800 graves, beneath what is now public housing.

The Tampa Bay Times published an investigation into what happened to the bodies of some of the people buried in Zion Cemetery in June.

“This is the third we have talked about in the last 12 months,” local historian Rodney Kite-Powell told the Tampa Bay Times. “There have to be more. People have lived in Tampa for a very long time."

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Ground penetrating radar revealed caskets underneath the land that is now the high school’s agricultural program.

Experts estimate that there could be as many as 250 graves lying three to five feet beneath the school.

In a statement, Hillsborough County Public Schools said it would be "delivering these findings to the county Medical Examiner and State Archaeologist today—as outlined in Florida law."