TULSA, Okla. (AP and KFOR) — Next week’s headline event marking the 100th anniversary of the Tulsa Race Massacre was canceled suddenly Thursday, with organizers citing “unexpected circumstances with entertainers and speakers.”

In a statement, the 1921 Tulsa Race Massacre Centennial Commission did not specify the circumstances that led to the cancellation of the event scheduled for Monday at ONEOK Field in Tulsa. The commission statement held out hope that it might be rescheduled later this year.

“Due to unexpected circumstances with entertainers and speakers, the Centennial Commission is unable to fulfill our high expectations for Monday afternoon’s commemoration event and has determined not to move forward with the event at this time,” the statement said.

The commission had enlisted Grammy-award-winning singer and songwriter John Legend to headline the “Remember & Rise” event Monday at ONEOK Field in Tulsa. Voting rights activist Stacey Abrams was to deliver the keynote address.

On Tuesday, President Joe Biden announced plans travel to Tulsa, Oklahoma to commemorate the 100th anniversary of the Tulsa Race Massacre on Tuesday, June 1. White House say the visit is still on.

The Department of Homeland Security today said the Tulsa Race Massacre commemoration events could be a target for white supremacists, according to local NewsNation affiliate KFOR, but said there were no credible threats.

Still, it said the security risk remained “heightened” since white supremacists, “historically have used simple tactics, such as vehicle ramming, small arms, edged weapons, and rudimentary explosive devices” and targeted events involving racial minorities or groups with opposing views.

“Remember & Rise” was to highlight a year of events the commission organized to educate people about the attack by a white mob that experts say killed up to 300 people, most of them Black.

Violence erupted May 31 and June 1 in 1921, when a white mob killed an estimated 300 people and wounded 800, most of them Black, while burning 30 blocks of Black-owned businesses and homes and neighborhood churches in the Greenwood neighborhood, also known as “ Black Wall Street.” Planes were even used to drop explosives on the area, burning it to the ground.

A renewed search for bodies in 2020 found at least 12 in an unmarked mass grave in a Tulsa cemetery. A team led by Oklahoma’s state archaeologist has not been identified the bodies or confirmed they are victims of the massacre. But they were found in an area adjacent to two gravestones of victims and where old funeral home records show both identified and unidentified victims were buried.