The district fenced off an area on the southern end of the campus and hired professionals to begin mapping and scanning it. The area had been used for the school's agricultural program. It contained lab facilities, a building and an open field for animals, a spokesperson for the school told NBC News.

The geophysical technicians eventually found "clear evidence of burials" in the area. A second area, in the northeastern part of the campus, was also scanned but did not show signs of any burials.

Although radar alone cannot identify exactly what is underground, the layout of the coffins is consistent with historical records and burial practices of the time, according to a report from the company that conducted the radar investigation.

The cemetery is believed to contain more than 250 graves. The school may not be able to identify all of the graves as some may have decayed too much to be detected by radar, and it's possible others could have been moved to another location. In addition, records show as many as 77 of the people buried in the cemetery were infants or young children, whose coffins would be difficult to find because of their size. Additional graves may also exist under the agricultural building.

Results from the GeoView ground penetrating radar technology that located 145 graves on the grounds of King High school in Tampa, Fla. GeoView, Inc.

The school district sent its findings to the county medical examiner and state archaeologist, who are expected to review the findings within 30 days and decide whether or not to return the land to the school. The school has plans to relocate the agricultural building in the area containing the graves, pending the outcome of the review.

Ridgewood Cemetery opened in 1942, and the school district purchased the land in 1959, according to the Associated Press.

In its press release, the school district said it would work with its Historical Response Committee, which was created in response to the discovery, to "discuss proper ways to memorialize the individuals, how to best care for the space and learning opportunities for students at King High School and other schools."