Helicopters, bloodhounds, hundreds of law enforcement personnel and an untold number of citizens are searching for a 7-year-old girl who never made home from school on Monday afternoon.

About 16 hours after Somer Renee Thompson was reported missing the Grove Park neighborhood of Orange Park, the Clay County Sheriff's Office and the Florida Department of Law Enforcement issued an Amber Alert for the child, Local 6 News partner WJXT reported.

Somer was last seen walking home from school with friends Monday afternoon. County officials met with the Florida Department of Law Enforcement and activated the statewide alert for missing children just before 9 a.m. Tuesday.

"We're hoping for the best, but we're working as if it is a crime scene," Clay County Sheriff Rick Beseler said at an 11:30 a.m. news conference. "Time is of the essence. Every moment that goes by is not in our favor. That's why the push is so hard."

Somer is described as 3 feet 5 inches tall and 65 pounds with brown hair in a ponytail with a red bow. She was last seen wearing a cranberry-colored sweat suit 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 siblings.

When Somer didn't arrive home Monday, her mother searched on her own at first, then flagged down a passing deputy to get help.

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 when Somer was reported missing Monday afternoon were still actively searching at midday Tuesday.

Tuesday morning, teams began searching 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.

The girl's father lives in North Carolina and has been contacted.

Beseler is asking 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 Thompson. 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 at Orange Park Junior High School at 1500 Gano Ave. to see how they can help.

In a parallel investigation, Beseler said they 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.