The hunt for graves at the Gaillard construction site suddenly got a lot more intriguing.

The number of sites is now at 37, officials said Friday, with the remains set out in what appear to be four closely aligned rows.

The pattern is likely proof that at some time in Charleston’s Colonial-era past there was a recognized cemetery on the site either forgotten or intentionally covered over as the city’s fledgling neighborhoods grew.

Of further intrigue: a single Revolutionary War-era cannon ball was found Thursday lodged in the dirt between two of the graves.

The ball measured about 4 inches in diameter and has a hole in the side where water had gathered.

It was not in danger of exploding and has been removed for study.

Lead archaeologist Eric Poplin said five sets of remains have been exhumed so far, offering curious, but not clear, insight on who is buried there.

Two of the skulls show copper staining, which could mark where a pin had been used to close a burial shroud, he said. No evidence of coffins or nails has been found. What is likely a small brass coat-sleeve button was also recovered.

Ever since the first two graves were discovered about two weeks ago when workers accidentally hit a buried skull, the number of suspected remains has continued to grow. The additional eight graves were found Thursday when the site’s perimeter was expanded.

“We moved the (excavation) pit back and we found a few more,” Poplin said. The four-row pattern shows the layout “actually makes a lot more sense and has a lot better shape,” he added. The four rows all run from east to west near the intersection of Anson and George streets.

The remains are about 10 feet below the surface under what had been part of the Gaillard Auditorium’s asphalt. Also in the area are at least two significant stone foundations belonging to buildings removed long ago, Poplin said.

“It’s pretty substantial,” he said of one of the walls.

Archaeologists say it is too early to determine who was buried at the scene, although the time period dates probably before 1750, or even as early as the 1720s. No headstones or markers have been found.

Poplin said he believes that based on the condition of the teeth in the remains, they do not belong to Native Americans.

The graves are mostly discernible as brownish-purplish rectangular stains that stand out against the surrounding sediment.

“I’ve been building for 40 years and I’ve never uncovered unknown grave sites as these,” added Bob Ferguson, senior vice president with Skanska, which is in charge of building the $142 million makeover of the new Gaillard Center.

The archaeological dig is on hold until next week, as heavy rains are expected in the coming days.

Reach Schuyler Kropf at 937-5551.