The FBI has now joined Ohio police in the investigation of the disappearance of 5-year-old Emily Rimel (search), who vanished from her bed early Tuesday morning.

Investigators are now treating the case as a kidnapping, after two days of searching with dogs and helicopters failed to turn up any trace of Emily. More than two dozen registered sex offenders that live around the area where the girl went missing are being questioned in the disappearance.

Authorities took a mattress, cushions, sheets and towels from the family apartment Wednesday as possible evidence.

Her mother’s boyfriend, Brent Copley, was the last person to see the girl after putting her to bed shortly after midnight. When her mother returned home from her overnight job, she found her daughter's bed empty.

Police say Copley has undergone polygraph and voice-stress analysis testing since the girl's disappearance. The results are being analyzed by the FBI (search).

Emily’s mom, Jane Rimel, told FOX News on Friday that she does not suspect her boyfriend had anything to do with the girl's abduction.

“No, I don’t, don’t think Brent had anything to do with it, he loves her like she is his own,” Rimel said. “I’ve never known him to do anything to harm my kids in any way.”

Warrants were filed to search undisclosed locations, as well as the car of Copley's friend, Lindsey Bruce, who had stayed at the apartment from Monday night until early Tuesday.

Police said no one has been ruled out as a suspect, nor has any motive been determined.

Officials are asking the public’s help and made a request for people to be on the look out for areas into which a small person would be able to crawl and not be seen or able to crawl out.

Searchers used dogs and a helicopter during a futile two-day search that combed a one-square-mile area of woods north of the Rimel apartment and near the Madison Elementary School, where Emily began attending kindergarten in September.

Emily is white, 3-feet tall and about 48 pounds, with brown hair and brown eyes. She was last seen wearing a red and orange striped shirt and purple spandex pants.

FOX News' Steve Brown contributed to this report.