ONSLOW COUNTY, N.C. -- The desperate search for a missing girl from southeastern North Carolina intensified Thursday.

3-year-old Mariah Woods was first reported missing from her Jacksonville home on Monday. Early Thursday morning, FBI Charlotte tweeted out a plea for anyone who had contact with the family on Sunday or Monday to call the Onslow County Sheriff's Office.

Onslow County Sheriff Hans Miller and the FBI held a joint press conference Thursday afternoon, saying they were proud of the coordinated effort between local, state and federal authorities. Miller said the community's outpouring of support has led investigators to allow citizens to join searches Friday.

In addition to volunteer groups, Miller said officers on horseback and on boats have joined the search for Mariah.

FBI Supervisor Stanley Meador said Mariah's family has cooperated with detectives during the investigation and that they located several "items of interest."

"Experts at the FBI lab in Quantico are testing items of interest that could help lead us to Mariah," Meador said. "As the family is cooperating, we are continuing to stay in contact as we need to."

Those items were flown to the lab by an aircraft provided by the U.S. Marine Corps.

NBC Charlotte learned more than 200 investigators have searched more than 100 acres in rural Onslow County, looking for Mariah.

Miller pleaded for the public to trust law enforcement's handling of the case as few details of the investigation have been made public.

"Some of the details have to be kept confidential because this is an active investigation," Miller said. "So I would respect our citizens to give us the respect and trust this is in good hands so we don't prematurely reveal anything that needs to be kept confidential because during any investigation, things change.

"We don't want to jeopardize our credibility by putting things out prematurely."

Mariah Woods. Submitted photo.

Here is a timeline of the events:

The mother's boyfriend told police he put Mariah to bed around midnight Monday. The next morning, the mother reported the little girl missing, an amber alert was issued and search teams were brought in to help.

On Tuesday, the FBI joined the search, bringing in helicopters, K9s and a dive team. On Wednesday, surveillance photos released from Walmart in Morehead City, believed to show Mariah with a woman, turned out not to be the missing girl.

Investigators called on residents in the southwest Verona area of Onslow County to join the search. People were being asked to check sheds, barns and wooded areas near their homes.

There was also a $2,500 reward posted for information.