BLAIRSVILLE, Ga. -- Professional searchers have taken over the hunt for a missing Gwinnett County hiker.

Volunteers have been barred from the rugged terrain where Meredith Emerson, 24, was last seen Tuesday.

Meanwhile, rescue workers and canine teams worked through the night and continued searching Friday morning for Emerson near Blood Mountain and for a man they described as a "person of interest" in her disappearance.

"The last team came at 6 o'clock this morning," Union County investigator Kimberly Verdone said Friday.

Verdone said multiple teams of search and rescue dogs, along with law enforcement officers and firefighters, were combing a 401 square mile area of rugged terrain.

Officials said they are seeking a "person of interest:" Gary Michael Hilton of DeKalb County in suburban Atlanta. They said Hilton, who is in his 60s, drives a 2000-2001 white Chevy Astro van. He was reportedly seen several times on New Year's Day with Emerson.

"It's not that, you know, he's a suspect. He is somebody that was last seen talking to her, last seen with her," Verdone said during a morning news conference.

She said investigators want to know when was the last time he saw Emerson and what they talked about.

Authorities said they have found a water bottle and a dog leash that belonged to Emerson.

One of Georgia's oldest and most popular state parks, Vogel State Park is located at the base of Blood Mountain in the Chattahoochee National Forest.

On Friday, the door of the park's Visitor's Center displayed "Missing Hiker" fliers with pictures of Emerson and her dog, posted by friends and family members.

Friends said Emerson went hiking with "Emma," her 1-year-old black Labrador retriever, on Tuesday. Her 1995 Chevrolet Cavalier was found abandoned Wednesday at the base of Blood Mountain.

Emerson, 24, is formerly of Longmont, Colo., and recently became a resident of Buford, Ga., in suburban Atlanta.

Her roommate, Julia Karrenbauer of Buford, said as many as 100 friends and family members have come to the park to aid in the search. Emerson's father, Dave Emerson of Longmont, Colo., headed to the mountain trails Friday with investigators and rescue workers to help look for his daughter.

"They're frightened, scared and we're all very hopeful," Karrenbauer said of Emerson's parents. "We're all trying to stay really positive here. It's been a really long three days."

Karrenbauer said Emerson is an experienced hiker with a blue belt in martial arts.

Tom and Peggy Hayduke of Seminole, Fla., said they have brought their four children to the park to hike for the last few years and were on the park's trails just a day before Emerson disappeared.

"It's a little scary," Peggy Hayduke said of the hiker's disappearance. But the Haydukes said they plan to return to the park next year.

Meanwhile, authorities have created a new tip line for people to submit information on the case. The number is 706-439-6069.