Officials have announced they have several leads in the search for the mass graves associated with the Tulsa Race Riot of 1921.

Three potential sites in the Oklahoma city were first identified in a state-commissioned report almost 20 years ago. It wasn’t until October of last year that investigators began reexamining potential long-lost gravesites after the mayor called them a “point of shame for our community,” reported a local NBC affiliate at the time. A series of ground-penetrating radar scans in recent months concludes the first phase of the search. The results, published in a 39-page report, suggest two key places that may contain the bodies of those killed in the massacre. The findings were presented in a live stream event hosted by members of the City of Tulsa and Public Oversight Committee, which includes descendants of those killed in the massacre, as well as a team of historians and scholars.

“It is important to understand how we got to this point tonight. First, it’s important to acknowledge that people have been putting in work on this for decades to get us to this step. There are great leaders in this community who did not allow this issue to fall into history or even not be recorded in history, which was the path it was headed on,” officials said at the presentation.

A newly discovered trench measuring around 9 by 7.5 meters (30 by 25 feet) is one of two potential sites. Experts say they are “confident” that this is a “very big candidate with something associated with the massacre”, though it is unclear how many bodies may lie underneath. Phoebe Stubblefield, a forensic anthropologist at the University of Florida, said at the meeting that the trench could contain anywhere from 10 to 100 bodies, but the level of preservation is unknown and therefore whether their identification is possible, NBC reports.

Long-buried in history books across the nation, the Tulsa Race Riot of 1921 is a deadly racial massacre recently brought back to attention by HBO’s “Watchmen”. On May 30, 1921, a young black man named Dick Rowland was riding in an elevator with a white woman named Sarah Page. Though historical accounts vary, Rowland was eventually accused of assaulting the woman in a newspaper report that ran the next day, inciting confrontation between racial lines, according to the Tulsa Historical Society and Museum. Confident that Rowland would be lynched for the accusation, dozens of volunteers from the affluent African Community known as the Greenwood District offered to guard Rowland at the courthouse overnight. (This thriving business district and residential area was so prominent that it had been known as the “Black Wall Street”.)

The men were faced with around 1,500 armed white men – most of whom were World War I veterans. Tensions escalated after gunfire erupted during the standoff, leading the Greenwood men to retreat to their community. White rioters led by the Ku Klux Klan followed, looting and burning the community to the ground. Within 24 hours, 35 city blocks lay in charred ruins and an estimated 800 people were treated for injuries.

The official death count was 36, but historians believe as many as 300 people may have lost their lives. To this day, their graves have never been found.

“The only way to move forward in our work to bring about reconciliation in Tulsa is by seeking the truth honestly. As we open this investigation 98 years later, there are both unknowns and truths to uncover. But we are committed to exploring what happened in 1921 through a collective and transparent process – filling gaps in our city’s history, and providing healing and justice to our community,” said Mayor G.T. Bynum in a statement.

If the mass graves are present and directly associated with the massacre, experts will determine how to properly store the remains and proceed with potential DNA testing and genealogical research. They will also explore commemorating the gravesites and honoring those who perished.