TULSA — Nearly a century after a brutal race massacre left as many as 300 black people dead, this city began to dig Monday for suspected mass graves from the violence.

A team of scientists, archaeologists and forensic anthropologists watched as a backhoe moved dirt from an 8-by-10-foot hole at the city-owned Oaklawn Cemetery, where ground-penetrating radar last year detected anomalies consistent with mass graves.

Several descendants of massacre survivors bore witness to the moment outside the graveyard’s wrought-iron fence, standing in a light rain after the work was briefly delayed by booming thunder and lightning.

J. Kavin Ross, whose great-grandfather owned a business that was destroyed in the massacre, said he had waited a long time for this day.

“I’ve waited for this day for over two decades to find out the truth of Tulsa’s public secrets,” said Ross, a photojournalist and teacher in Tulsa who spent years of his own time interviewing survivors of the massacre. “A lot of people knew about it but wouldn’t tell about it.”

Tulsa Mayor G.T. Bynum (R), who ordered the investigation reopened after a Washington Post story detailed the unresolved questions surrounding the violence, told reporters that he once thought it was incredible that there could be mass graves in Tulsa.

“You hear about mass graves in authoritarian regimes,” he said. “You don’t hear about them in the United States and definitely shouldn’t be hearing about them in Tulsa.”

The excavation was delayed for three months by the coronavirus pandemic.

It comes weeks after President Trump appeared in Tulsa at a campaign rally that drew more than 6,000 people to an indoor arena, where few wore masks. Tulsa Health Department Executive Director Bruce Dart said last week that a spike in new coronavirus cases in Tulsa may be linked to Trump’s rally and the protests it generated.

But Bynum decided not to postpone the work at Oaklawn a second time. He called the investigation personal for him. “I don’t want my kids growing up in a city where we might be walking around on mass graves, and we haven’t done everything we could to find them and identify the victims,” he said.

Although the scientists said their radar findings are promising, the only way to determine precisely what lies beneath the ground is to dig. The excavation will take up to two weeks.

In the trench, archeologists found pottery pieces, glass items, metal bowl, an oven door and buttons dating back to 1920s.

Phoebe Stubblefield, a forensic anthropologist from the University of Florida, said she’s hopeful that any bones found will be preserved well enough to “allow us to extract DNA from remains” that could help identify the victims and connect them to descendants.

She said she would be looking for intact bones. She will also be looking for any signs of violence or trauma, or charred remains.

The backhoe is moving slowly so as not to crush any bones that may be in the trench. Stubblefield said she expects the backhoe to dig 4 to 5 feet before hitting any potential remains.

The rest of the excavation will be done by hand. If the city finds unmarked human remains at the site, the state medical examiner’s office will begin an investigation to determine how the person died.

“The cause of death determination would be an important step to the investigation as remains will be close to 100 years old and a Spanish Influenza outbreak occurred in Tulsa in 1919 prior to the Race Massacre in 1921,” city officials said in a statement.

The city is expected to issue daily updates on the excavation.

The work comes nearly seven months after a team of forensic anthropologists and archaeologists, led by the Oklahoma Archaeological Survey at the University of Oklahoma, announced that they had found “possible common graves” at two sites in Tulsa.

They identified the sites as the Canes, located on a bluff along the Arkansas River near Highway 75, and the Sexton area of Oaklawn Cemetery, which is a few blocks from Greenwood, the black community that was destroyed during one of the worst episodes of racial violence in U.S. history.

The massacre began May 31, 1921, after a black teenager, who was working as a shoe shiner in downtown Tulsa, was accused of assaulting a white woman in an elevator. A white mob marched on Greenwood, one of the most affluent black communities in the country.

Historians believe that as many as 300 black people were killed, and 40 square blocks of what was known as Black Wall Street were destroyed by fire. The destruction included more than 1,250 homes, churches, schools, businesses, a hospital and library.

Survivors reported seeing bodies tossed into the muddy Arkansas River or loaded onto trucks or trains, making it difficult to account for the dead.

For decades afterward, people in Tulsa avoided discussing what had happened. No one was ever arrested for the violence. But Bynum has said it is time to find out whether there are mass graves, especially as the city prepares to mark the 100th anniversary of the massacre.

“There was a concerted coverup by city leaders and business leaders” to hide what happened, he said. “Anytime a terrible event occurs, there are two inclinations. One is to find out what happened and why. The other inclination is to cover it up. Unfortunately, the leaders in Tulsa in 1921 chose that second option. You had generations who never heard about the massacre because the conspiracy of silence was strong."

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