Florida officials expanded their search for a 7-year-old girl who vanished while walking home from school Monday afternoon.

Somer Thompson was released from Grove Park Elementary School in Grove Park, in northern Florida at 2:50 p.m. She was with her twin brother, her 10-year-old sister and friends when she reportedly ran ahead of them after getting into a fight. Her brother and sister said she was not at home when they arrived at 3:05 p.m.

Somer's mother's boyfriend searched up and down the block for her when she didn't come home; her mother called home at 4 p.m. to check on the kids and immediately called authorities.

Clay County Sheriff Rick Beseler said officers are investigating whether Somer's disappearance is connected to an event that happened in the area on Oct. 10, when three people unsuccessfully tried to lure a 5-year-old girl into a car.

"We want to emphasize while we're taking this into consideration, we are not focusing just on this … we're exploring other areas and angles,” Beseler said.

He said 57 sex offenders have been interviewed within a 3-mile radius, and their homes and yards have been searched. The search was expanded Tuesday to a 5-mile radius, and officials say they will interview 30 more registered sex offenders.

"This is an all-out search," Sgt. Dan Mahla, of the Clay County Sheriff's Department said at a news conference Tuesday afternoon. "We are going to keep trying and trying and trying. We have all these resources and we are maximizing them to the max."

He said they've received 200 leads in the case, but no person of interest.

"She is an endangered, missing child." Mahla said. "It would be very tough for her to survive [given her age, location and conditions outside], so we suspect foul play."

More than 100 Clay County deputies were searching for the second-grader on Tuesday. Beseler said the area where Somer disappeared is wooded and swampy, and they want to search the woods thoroughly before moving search units out farther. Dogs and helicopters are being used.

Thompson 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.

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

Foxnews.com's Michelle Maskaly contributed to this report.

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