ORANGE PARK, Fla. -- More than twenty-four hours after a 7-year-old failed to come home from school, helicopters, bloodhounds and mounted deputies had joined a least 100 law enforcement personnel and an untold number of citizens in a massive search for the girl.

An Amber Alert was issued Tuesday morning for Somer Renee Thompson, who was reported missing from her Grove Park neighborhood of Orange Park about 4 p.m. Monday.

By Tuesday afternoon, after following 80 leads and searching several square miles of Orange Park with no sign of Somer, investigators were increasingly concerned for her welfare.

"She is definitely endangered and we do suspect foul play," Clay County Sheriff's Office Sgt. Dan Mahla said at a 4 p.m. briefing.

Somer is described as 3 feet 5 inches tall and 65 pounds with brown hair in a pony tail with a red bow. She was last seen wearing a cranberry-colored sweatsuit with pink stripe on the sleeve and pants. She also had a black, pink and white backpack with a skull and hearts. She may be wearing a white hat and scarf.

Deputies said the second-grader was last seen at 2:45 p.m. walking home from Grove Park Elementary School near West Gano Avenue and Debarry Avenue with her twin brother and her sister. Authorities were told she ran ahead of them after "a childhood squabble" with her twin brother.

When Somer wasn't home by 4 p.m., her mother called police.

"We're hoping for the best, but we're working as if it is a crime scene," Clay County Sheriff Rick Beseler said Tuesday morning. "Time is of the essence. Every moment that goes by is not in our favor. That's why the push is so hard."

Beseler said deputies were out all night using infrared cameras and dog teams to search the wooded areas. Beseler said when deputies finished interviewing the 58 registered sex offenders within three miles of where Somer disappeared; they expanded the search to a five-mile radius.

Beseler said some of his deputies who were ending their shifts Monday when Somer was reported missing Monday afternoon were still actively searching at midday Tuesday. By 4 p.m. crews were transitioning to a 12-hour rotation.

Tuesday morning, teams search wooded areas within the one-mile radius for a second time as well as searching a larger area.

"We still don't have any indication that is an abduction, but working on the assumption that a 7-year-old would not be gone for this length of time, we have been able to meet the criteria for an Amber Alert notification," Beseler said.

Somer's mother, Deana Thompson, came out of the house once Tuesday to talk to the media, but was overcome with emotion before she could make a statement. Her mother spoke through tears on behalf of the family.

"You think about this and you think this can't be happening to me; this can't be happening to my family," Debbie Bowling said of Deana Thompson. "It's very hard."

Beseler visited the family to assure her the sheriff's office was doing everything possible to find Somer.

"She was gratified that hundreds of people have come out to help," Beseler said.

Somer's father, who lives in North Carolina, told Channel 4 he got a phone call from the Clay County Sheriff's Office Monday night that his daughter was missing.

"Don't freak out, but we're trying to find your little girl," Samuel Thompson said he was told in the 6:30 p.m. call.

"She's independent," Thompson said of Somer. "If she was mad ... she's got a temper."

He said he talked to his estranged wife and encouraged her to stay positive.

"As each hour goes by, she gets less and less hopeful," Bowling said of Somer's mother. "She keeps saying she wish she could wake up and it was all just a terrible dream."

Neighbors Asked To Help

Early Tuesday, Beseler asked residents in the Grove Park area to look through their yards, parked cars and adjacent properties. He asked if you see anything unusual, including a backpack, clothing or shoes, to not pick them up, but call the sheriff's office at 904-264-6512 or call 911.

Beseler asked that volunteers not go into wooded areas before they can search them with dogs looking for the girl's scent.

Deputies and detectives from every branch of the Clay County Sheriff's Office -- about 100 personnel -- were looking for Somer. Additional support is also being provided by the St. Johns and the Jacksonville Sheriff's Office. The FBI has also assigned a member to assist Clay County, along with staff from the FDLE.

At daylight Tuesday, a helicopter with the Florida Fish and Wildlife Conservation Commission joined the search efforts.

The Clay County Sheriff's Office has utilized reverse 911 as well as the school system's automated phone message system to get information about Somer to as many households as possible as quickly as possible.

Dozens, perhaps hundreds of neighbors and citizens from as far away as Jacksonville and Middleburg were passing out fliers and showing up at the sheriff's office command post to see how they can help.

To read more about the help and search efforts from volunteers in the community, go to Community Searches For Missing Girl.

Abduction Attempt Nearby 10 Days Ago

In a parallel investigation, Beseler said detectives were looking into an incident 10 days ago when three people in a blue Nissan allegedly tried to lure a girl into their car. The Orange Park Police Department report said a 5-year-old girl on a bicycle was riding about one block from where Somer was last seen when she was approached by a vehicle driven by a Hispanic woman with two Hispanic men as passengers.

According to the report the three approached the 5-year-old in the 1200 block of Ambor Circle Drive and told her to get into the vehicle. When she screamed and rode her bike in the opposite direction, the car sped off in an unknown direction.

"We have no reason to believe that that incident is connected to the disappearance of Somer, but we cannot assume that it is not connected either, so we're working on any leads we can follow up," Beseler said.

April Boothroyd, is the mother of the 5-year-old, and Shannon Pollett, the woman who stopped her vehicle during the abduction attempt, appeared with Beseler at Tuesday morning's news conference.

Pollett said the girl was "screaming, no, no, no, and she was visibly upset." The car sped off when Pollett stopped, and she followed the girl home to tell her parents what had happened.

"God was on our side that day," Boothroyd said.

To read more on the nearby abduction attempt, go to Abduction Attempted 10 Days Ago.

'Somer Is One Of Ours. We Want Her Home Safely'

Prior to students arriving Tuesday morning, Grove Park Principal Lynda Braxton urged her faculty and staff to report anything and everything they may know about Somer’s whereabouts -- even the smallest detail.

Investigators were in and out of the school throughout the day talking to administrators, teachers and students. School officials said they were do everything possible to help.

“Somer is one of ours. We want her home safely,” Braxton said.