By Marlene Lenthang—
NBC News
The search for a 13-year-old girl missing in Florida since Monday morning is redoubling, following the arrest of her mother's boyfriend, whom police call the "main suspect."
Madeline Soto was last seen around 8:30 a.m. when the man allegedly dropped her off a few blocks from Hunter's Creek School in Orlando, according to Orange County Sheriff John Mina.
Madeline SotoOrange County Sheriff's Office
At 4:30 in the afternoon, when the mother went to pick her up from school, she found out that her daughter never arrived there, and had left her phone at home.
That night the search for the girl began.
Stephan Sterns, 37, was arrested Wednesday night for sexual assault and possession of child sexual abuse material.
Although he was not arrested in direct connection with the disappearance of the young woman, the Orange County Sheriff's Office stated that "he is considered
the primary suspect at this time."
During the investigation, detectives discovered “disturbing images” and videos of a “criminal and sexual nature” in a forensic analysis of Sterns' phone, according to the Sheriff's Office.
They claimed Stern tried to erase evidence.
It was determined that these crimes were committed at the family's home in Kissimmee and local police, who are handling the case as sexual assault, were notified.
The Sheriff's Office shared a video showing Sterns being quietly placed into a police car.
He was questioned Wednesday night by Kissimmee police and Sheriff's Office deputies.
The man asked for a lawyer and was placed under arrest
and taken to jail, authorities said.
“He had the opportunity tonight to open up to detectives and help them find information about Maddie's disappearance,” the sheriff added.
“Their loved ones deserve answers,” he added, promising not to stop until he finds the teenager.
[A neighbor of the 11-year-old girl missing in Texas was identified as a person of interest]
A police dog smelled an object belonging to the young woman on Monday night and an “exhaustive search” was carried out that led to no results.
Detectives accessed her phone and found information “that indicated that, when she turned 13 on February 22, she told several people that she
wanted to go live in the forest
,” Mina said.
More than 100 agents, detectives, intelligence analysts and bloodhounds have searched for her, including in a wooded area near the school.
The sheriff said Wednesday afternoon that the girl's family home in Kissimmee was being monitored until police could obtain search warrants.
The young woman has been described as blonde with blue eyes and 5 feet and one inch tall;
She was last seen wearing a green sweatshirt, black shorts and white Crocs.
Anyone with information on her whereabouts is asked to call her at 911 or the Sheriff's Office.