Sheriff Hans Miller made the announcement Saturday night and said that the family has been notified that her body has been found.
UPDATE: Her body was found by divers in Pender County creek, 25 miles from her home.
Investigators said in a Saturday morning press release that they believed Mariah was deceased, and her mother's boyfriend was arrested.
Earl Kimrey, 32, has been charged with concealing of death, obstruction of justice, second degree burglary, felony larceny, and possession of stolen property.
Kimrey is the live-in-boyfriend of Kristy Woods, who is Mariah’s mother.
The warrant for Kimrey says he obstructed justice by "removing Mariah Woods' body from the scene of her death and did conceal Mariah Woods' death and body, knowing that Mariah Woods died from unnatural causes. The defendant acted with deceit and intent to fraud."
Kimrey said he spoke to Mariah when she woke up around midnight, and that he told the child to go back to bed. Authorities said he was the last person to see her.
Two other children, Kristy’s five and ten-year-old sons, were also in the home when Mariah disappeared.
Searchers have walked countless miles, and also used horses, boats, drones, and divers with underwater sonar in efforts to locate the missing toddler.
“Due to evidence gathered during the course of the investigation, it is believed that Mariah is deceased,” the Onslow County Sheriff’s Office said early Saturday. “At this time, the location of Mariah is unknown. The searches will now shift to a recovery process.”
On Tuesday, Mariah’s biological father, Alex Woods, told WTCI that Kristy had not allowed him to see his daughter for a year before her disappearance, despite a custody agreement he claims gave him weekend visitation.
Alex is also the biological father of Kristy’s two sons.
He said he first heard about his daughter’s disappearance in a radio alert, and that he doesn’t understand how Mariah could have been abducted from the home without anyone noticing.
"Somebody just, walked right up in there, grabbed the three-year-old out the bed - she didn't cry, she didn't scream. Nobody heard nothing?" he questioned.
Alex told WTCI he believed Kristy and Kimrey had “something to do with it.”
He received a similar sentence following convictions for assault or threatening of a government official and being drunk and disorderly in 2012.
In 2015, Kimrey was again convicted of larceny, and received another term of probation with a suspended jail sentence.
Kimrey is being held at the Onslow County jail on $1,010,000 bond. Authorities said on Saturday that additional charges may be filed as investigation continues.