Archaeologists at Magnolia Springs State Park might have hit pay dirt in the form of charred wood from the stockade wall of a Civil War prison camp.

"We found a change in the soil pattern, with some charred wood in it, that is a strong indicator we were at or near the stockade wall," said Crystal Paulk-Buchanan, a Georgia Department of Transportation spokeswoman.

The two-day dig, undertaken by Georgia DOT, the National Park Service and other groups, was aimed at learning more about Camp Lawton, where 10,299 Union prisoners of war were housed in fall of 1864.

The camp was built near Millen in the closing months of the war on property now occupied by the state park.

One of the site's perennial mysteries involves how many prisoners died and were buried there during the camp's brief existence. Scant historical records indicate 685 prisoners were buried at the site before being reburied at a national cemetery in Beaufort, S.C., after the war.

However, a Union soldier's diaries, which surfaced in Virginia in the 1990s, include anecdotal - but firsthand - accounts of life at Camp Lawton, including the deaths of 1,300 prisoners.

Studies were first launched in 2005, when DOT archaeologists used ground-penetrating radar in efforts to identify changes and structures beneath the ground.

This week, archaeologists began digging in areas where the radar indicated anomalies.

"It's promising, but they still have to do some data analysis," Ms. Paulk-Buchanan said. "We'll have to go back out there later this year to do more work."

The primary objective of the studies includes mapping the lines of the stockade walls, which were made of logs and earthen embankments.

Those lines, in turn, could help locate entrances, access roads and other features of the camp.