Investigators said they have no clues three days after a 7-year-old girl in North Florida disappeared while walking home from school, as the girl's mother made a tearful plea for the child's return.

Somer Thompson's mother Dina said she assumes someone has her daughter. Police suspect foul play after initial thoughts that she had fallen into something or had gotten lost did not return any results.

Thompson made an appeal to Somer's possible abductors.

"Just drop her off somewhere. I don't care if you ever get in trouble," Thompson said. "I just want my baby back."

SLIDESHOW: Somer Thompson Disappears on Walk Home From School.

Clay County Sheriff Rick Beseler said investigators are baffled. He said officers have expanded the initial search area and interviewed about 75 known sex offenders in a five-square-mile radius. Teams of volunteers are walking arm-to-arm through the woods, and deputies are using helicopters and search dogs.

"We just really need a break in this case. We need a tip, we need a phone call," Beseler said. "Somebody knows where Somer is, and we need that person to call us."

The girl vanished on her mile-long walk home from school Monday in Orange Park, near Jacksonville.

More than 100 Clay County deputies, law enforcement officers from neighboring counties, the FBI and the Florida Department of Law Enforcement have scoured a residential Orange Park neighborhood looking for Somer.

The investigation has produced more than 150 leads, but officials remain baffled as to her whereabouts.

Thompson said Somer was squabbling with another child, and her sister told her to stop. The girl got upset, walked ahead of the group and wasn't seen again.

Beseler said officers have determined that Somer's disappearance is not connected to an event that happened in the area on Oct. 10, when three people reportedly tried and failed to lure a 5-year-old girl into a car.

"Investigators located that car and those individuals," Beseler said. "We are confident that incident had nothing to do with Somer's disappearance. But I can't go into any further details about that until we finish our investigation."

Clay County Public Information Officer Mary Justino said the persons of interest in that came forward Tuesday when they heard about Somer's disappearance.

"We were able to rule out that they were attempting to abduct the other child," Justino said. "We believe that their reason for stopping was the same reason the other woman stopped; they were checking on the child who was crying and who appeared to have fallen off her bike. The matter is not yet closed but we believe there was no ill-intent as to the interaction between the child and the people in the blue vehicle."

Somer is white, 3 feet 5 inches tall and weighs 65 pounds. She has brown hair that was in a pony tail and was wearing a cranberry colored jumpsuit with pink stripes and a black T-shirt underneath. Her backpack is black with pink and white skulls and crossbones.

Her mother said she has an "odd-shaped" birth mark on her left shin.

People are encouraged to call the tip line at (877) 227-6911 with any additional information on the child’s whereabouts.

The Associated Press contributed to this report.

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