Within moments of resuming the search for graves at the Gaillard Auditorium, archaeologist Eric Poplin hit on three more.

On any other day, that might be a big deal. But Poplin soon had to find a lot more orange marking flags.

The grounds of the Gaillard resembled a dig worthy of National Geographic consideration Thursday after at least 25 graves were uncovered in the earth near the corner of George and Anson streets.

Two more areas were listed as “probable” hits.

Whom the graves hold or how they got there remains a mystery, since no known cemetery is recorded for that site.

Based on preliminary research, Poplin said the pits date to at least 1780, the time of the American Revolution, and possibly much earlier.

What city officials plan to do once all the graves are counted is unclear. Staff members were talking with lawyers about the city’s responsibilities in connection to the $142 million Gaillard makeover.

“It might be a day or two before we have a plan of what to do,” said Dustin Clemens, Charleston’s assistant director of capital projects.

The graves, spread out in two distinct and even rows, emerged after a combination of heavy machine, shovel and trowel work removed tons of dirt to open an area previously sealed under a Gaillard parking lot.

By Thursday afternoon, a flat-bottomed pit about 70 feet long by 30 feet wide had been cleared to a depth of 10 feet. On the ground were flags marking some two dozen squared-off purple-brown rectangular stains.

The stains probably don’t depict actual coffins in the ground but instead represent the original soil that was turned over to fill in each grave all those decades ago.

The dark color is also probably heavily influenced by the decaying bodies that were put inside since they were full of nutrients that attracted all sorts of plant life, Poplin said.

At least one of the graves is near the foundation of a long-disappeared building or house, prompting Poplin to theorize that the burials were done long before the structure was put in.

It “implies the people who built the house didn’t know the graves were there,” he said. “Or didn’t care.”

While maps of the area don’t show a recognized cemetery ever being on the site, officials do concede older city maps may simply be unreliable as to what Charleston looked like so long ago.

The dead might have been civilians, sailors, slaves or soldiers, but clues about that may also have to wait until all the remains are removed and studied off-site for their sex and age.

Trinkets possibly buried with the dead could also help with identification, but so far no artifacts or even coffin nails have been found. The deceased may have gone into the ground wrapped only in shrouds.

“If they are related to the Revolutionary War, they could be soldiers,” Poplin said.

Some evidence of Charleston life from the time also has been uncovered, but it’s mostly been shards of broken dishes or plates, bottles and animal bones. “Domestic refuse,” Poplin called them.

During the dig Thursday, some human bone remains were exposed, but by accident.

Evidence of the graves was uncovered last week when workers were digging a trench for a drain system tied to the Gaillard improvements. At the time, only two grave sites were found, and further excavation was put on hold because of the recent heavy rain. Thursday turned out to be dry.

Charleston has a history of uncovering forgotten grave sites as new and modern construction is launched. But the significance of this find is that the site is considered close to the original Colonial heart of the city, before the march up the peninsula took off in later centuries.

The dig may resume today, but that depends on decisions about the next steps to take. In the meantime, security guards have been hired to watch over the open dig pit.

Reach Schuyler Kropf at 937-5551.