BLAIRSVILLE, Georgia (CNN) -- The man last seen with missing hiker Meredith Emerson in the north Georgia mountains is in custody and is being questioned by the Georgia Bureau of Investigation, authorities announced Friday evening.
Gary Michael Hilton, 61, was detained after a police officer spotted his van at a convenience store in suburban Atlanta.
Investigators also have another piece of the puzzle: Emerson's black Labrador retriever, Ella.
The dog walked into a grocery store about 30 miles north of Atlanta hours before Hilton was spotted Friday.
The animal was positively identified through an implanted microchip. Watch how the dog was discovered »
Emerson's roommate, Julia Karrenbauer, said she's encouraged that Hilton has been found and still hopeful "that [Emerson] walks right into that same damn Kroger that her dog did."
The search for Emerson will continue Saturday morning, said Union County sheriff's investigator Kimberly Verdone.
No criminal charges have been filed in the case, she said.
Earlier Friday, a Georgia State Police helicopter and search dogs joined in the effort to find 24-year-old Emerson, which now spans 400 square miles.
She was last seen hiking along the Freeman Trail on Blood Mountain on New Year's Day.
Witnesses saw Hilton and his reddish dog with Emerson on "multiple occasions" Tuesday before she disappeared, Verdone said.
Before Hilton was found Friday, a spokeswoman for the Emerson family was asked what she'd like to say to Hilton, who police said was a person of interest and was not considered a suspect.
"We need him to come forward. We need him so much to do that, to give us that missing link of information that we need," said Peggy Bailey.
"Please, please, if you could -- and I speak to him and to anyone that could contact him -- if you've been hesitant, please don't be hesitant. If you've been worried that you didn't want to share some information, please set that aside and have the courage to come forward. We need you," Bailey said.
Emerson was reported missing Wednesday. Her parents flew from Colorado to Georgia the same night, a family spokeswoman said. Watch what police know so far »
"At one time they were seen talking and let the dogs run loose; the dogs ran up the mountain, and they followed them afterwards," Verdone said of Hilton and Emerson. Watch Verdone describe scope of Friday's search »
A witness noted the license plate on a 2001 Chevrolet Astro minivan registered to Hilton in DeKalb County, Georgia, Verdone said. The Georgia Bureau of Investigation said a second white 1996 Astro van is registered to Hilton, also in DeKalb County, where Hilton was picked up.
On Thursday, Verdone said police confirmed that a water bottle and a leash found in the area belonged to Emerson. The young woman's vehicle also was found at the head of the 6-mile Freedom Trail -- which is part of the Appalachian Trail -- Verdone said Wednesday.
Karrenbauer said Thursday that Emerson's sunglasses and mittens were found in the area, as was a baton. Watch as roommate describes Emerson »
Verdone did not confirm those reports. She said Emerson, whom she described as "familiar with hiking," had been dressed for the cold weather Tuesday.
Bailey described the blond, 5-foot-4, 120-pound woman as "athletic," "feisty" and "level-headed."
"Meredith Emerson could do anything," she said. "I'm praying hard."
Emerson's parents are "devastated and frightened," Bailey said. "They're waiting as we all are."
Verdone urged people with information regarding the young woman to call (706) 439-6066. E-mail to a friend
CNN's Marylynn Ryan and Michael Phelan contributed to this report.
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