Authorities said Meredith Emerson, 24, has not been seen since midday Tuesday, when she and her black Labrador, Ella, set off on a trail just south of Vogel State Park near Blairsville.

Now officials are trying to determine whether a DeKalb County man might have had something to do with her disappearance. Witnesses reported Thursday that they had last seen her on the trail with another hiker, a rather dishevelled-looking man in his 60s.

Kimberly Verdone, spokeswoman for the Union County Sheriff’s Office, said Thursday morning that the man had been named a "person of interest" in the case.

By 6 p.m. Thursday, authorities had identified the man as Gary Michael Hilton, 60. Vehicle registration records show that Hilton owns a white Chevrolet Astro van with DeKalb County plates and the license number AFQ 1310. Police believe he may be driving that van.

"He was seen talking to (Emerson) numerous times Tuesday," Verdone said.

She described him as white, about 160 pounds, and about 5 feet, 9 inches tall, with "bad teeth." He was reportedly wearing a large backpack and a yellow jacket with black patches on the elbows.

"He also had a reddish, retriever-type dog that answered to the name ‘Danny.’" Verdone said.

Emerson’s Chevy Cavalier was discovered at the trailhead early Wednesday morning. Union County officials initiated a ground search of the area, but strong winds prevented a Georgia State Patrol helicopter from performing an aerial search Wednesday.

Charles Worden, Union’s fire chief and emergency management director, said the chopper was able to take off around 8:30 a.m. Thursday.

"We first had to clear the woods of people, because they would show up on the infrared (a device that detects body heat) and confuse the search," he said.

By noon, they had sent three search teams into the forest, including dozens of volunteers working under the direction of the Georgia Department of Natural Resources’ search-and-rescue experts.

The assumption was that if Emerson was still in the woods, she must have been somehow injured or immobilized. Friends and family found it hard to believe that she could have simply become lost.

Emerson grew up in Longmont, Colo., and was an experienced hiker and athlete, well acquainted with wintry weather. She moved to Georgia to attend the University of Georgia, where she graduated in 2005 with a degree in French. She works as an account manager at Progress Container & Display in Winder.

Emerson was apparently last seen on the Freeman Trail, a rocky, 1.9-mile spur that connects two sections of the Appalachian Trail south of Blood Mountain.

Searchers have found a water bottle and a dog leash near a hiking trail, and police confirmed that the items belonged to Emerson.

Because of the suspicious circumstances of the case, Union County authorities requested help from the Georgia Bureau of Investigation, which sent several agents to the site Thursday morning.

Authorities have not said they have any reason to believe that Emerson is currently with Hilton.

But Mark Warren, who runs the Medicine Bow wilderness survival school near Dahlonega, said if Emerson somehow traveled away from Blood Mountain and is in another place, at least she might no longer risk the dangers of exposure to extreme cold.

Temperatures on Blood Mountain dropped almost to single digits Tuesday and Wednesday night, with wind-chill readings near zero. Warren said even a warmly clothed person would quickly succumb to hypothermia under such conditions.

"To last two nights in that kind of weather seems almost impossible, I’m afraid," he said.

Still, Emerson is said to have formidable outdoor skills and knew how to handle herself in the wilderness.

"She could survive by making a construction of leaves and sticks and getting inside to trap her own body heat," Warren said. "The other way would be to create a source of external heat by building a fire."

But the fierce winds, and the 2 inches of snow that fell on Blood Mountain Tuesday night, would have made it difficult to keep a fire lit.

And while Emerson’s canine companion, Ella, might provide emotional comfort, "Just cuddling with the dog would not provide much warmth," Warren said.

"The strong wind is the main issue. It removes heat from your body so quickly, there would be almost no chance of survival if a person did not have access to shelter."

Anyone who has information about either Emerson or Hilton is asked to call the Union County Sheriff’s Office, 706-439-6066.