(CNN)Crews searching an excavation site at Oaklawn Cemetery for the remains of those killed in the 1921 Tulsa Race Massacre found five coffins on Thursday afternoon.
This brings the total amount of coffins found at the "mass grave feature" to 20 thus far, according to the city of Tulsa.
After conducting the majority of the groundwork this week, the formal exhumation process is expected to start on Monday, June 7, the city said in a statement.
An eight-member team from the Tampa, Florida, office of Cardno Inc., an environmental and infrastructure company, is expected to be at Oaklawn Cemetery up to six to eight weeks completing the exhumation process.
"This is going to be a longer process, so we're just at the very beginning of that stage," said Kary Stackelbeck, the Oklahoma state archaeologist, in a video update posted to Facebook. "The analytical component of this is actually going to take a fair bit longer for us to start getting some of those answers with regard to the individuals that are contained within these coffins."
Oaklawn Cemetery will serve as a temporary burial site for any remains found, and a public oversight committee will make recommendations for a permanent burial and memorial location for any 1921 Tulsa Race Massacre victims identified during this process.
Experts led in part by the Oklahoma Archaeological Survey began mapping and prepping the site on Tuesday near the headstones of massacre victims Eddie Lockard and Reuben Everett.
Though ground-penetrating radar identified 12 coffins, a funeral home ledger suggests there may be 18 bodies in the area. The excavation team is preparing for the possibility of finding as many as 30.
Heavy machinery will scrape off the first few feet of topsoil to begin the process.
"There may also be some hand-excavation, use of metal detectors, and screening of excavated soil -- depending on what is discovered during the first day," according to details released by the city. "At the same time, other research team members will be working to set up on-site workstations for artifact processing and laboratory analyses."
Once the bodies are exhumed, the city and its public oversight committee will determine the next steps for "storing remains, DNA testing and genealogical research, and commemorating the gravesites and honoring the remains," said a city news release.
The work — which will unfold behind a screening fence with researchers, cultural monitors, historians, morticians, a forensic anthropologist and a videographer — may take months, the city says. That's not counting the efforts to identify the bodies and determine if they are indeed victims of the massacre.