Hampton, a native of Homosassa, Fla., where the girl lives, offered a $25,000 reward Saturday for any information leading to the location and return of Jessica Marie Lunsford.
Meanwhile, more than 250 people gathered at a local church Saturday morning to join the search for Jessica. Buses took groups of the volunteers to the woods and marshes of western Citrus County, about 60 miles north of Tampa. Some searched on foot while others rode horses and all-terrain vehicles.
Investigators had received more than 150 tips but almost no clues.
Citrus County Sheriff Jeff Dawsy said investigators are re-interviewing Jessica's friends and re-examining all the leads they have to see if there is "anything we missed."
Jessica lives with her father, Mark Lunsford, and his parents and hasn't been seen since Wednesday night when her grandmother tucked her into bed. Her mother lives in Ohio.
Lunsford told authorities he had returned Thursday morning from a girlfriend's home and was getting ready for work when he realized his daughter's alarm clock was sounding and she wasn't there. The clothes she had laid out for school were still in place and none of her shoes were gone. However, one of her dolls was missing, Dawsy said Friday.
"It amazes me we haven't uncovered anything to take us in a specific direction," Dawsy said Friday. "That's the most frustrating thing."
Lunsford said Saturday that he is convinced his daughter was abducted but he can't understand how or why. He said his mother woke up Saturday screaming for the missing girl.
"I have so many questions in my mind," he said. "How do you do that? How did someone come in and get my daughter? I just can't imagine. How did it happen? How do you do that?"
Jessica's mother, Angela Bryant, has remarried, has a 5-year-old son and lives in Morrow, Ohio. She was interviewed by the FBI. "I don't know where she is," Bryant, 31, said in a tearful telephone interview Friday.
Information from The Associated Press was used in this report.