OKLAHOMA CITY (AP) — At least 10 bodies have been found in an unmarked mass grave at a Tulsa cemetery where investigators are searching for remains of victims of the 1921 Tulsa Race Massacre, a state official said Wednesday.

“What we were finding was an indication that we were inside a large area ... a large hole that had been excavated and into which several individuals had been placed and buried in that location. This constitutes a mass grave,” said Oklahoma state archaeologist Kary Stackelbeck.

There were 10 coffins discovered with what is presumed to be one person in each coffin, Stackelbeck said. She said further examination is needed.

The massacre left an estimated 300 mostly Black Tulsa residents dead and 800 more wounded. The massacre — which happened two years after what is known as the “Red Summer,” when hundreds of African Americans died at the hands of white mobs in violence around the U.S. —- has been depicted in recent HBO shows “Watchmen” and “Lovecraft County.”

Forensic anthropologist Phoebe Stubblefield, a descendant of a survivor of the massacre who is assisting in the search, said it would take considerable time to identify the remains and determine whether they were victims of the massacre.

The search began Monday and is the second this year after an unsuccessful search in another area of the cemetery ended in July.