Zahra's stepmother, Elisa Baker, was jailed on a felony obstruction of justice charge the same day. Baker was already in custody, having been arrested over the weekend on several charges unrelated to her stepdaughter's disappearance.
Though police said she admitted Tuesday to writing a ransom note after demanding $1 million, she has since denied she had anything to do with Zahra's disappearance.
In many of the high-profile missing children's cases, such as Chelsea King's or Elizabeth Smart's, the family becomes an ally to authorities.
That's not necessarily the case in Zahra Baker's.
Though Hickory police have told local media that Zahra's father, Adam Baker, had cooperated he still remains an unofficial suspect for some, along with his wife.
But, Allen noted, "you always look at those closest to the child first."
In an interview with The Associated Press, Baker said he was unsure if his wife was involved in the disappearance. "I'm still trying to figure it all out ... I just want to find her."
Since news of Zahra's case went public, neighbors and one relative have come forward to say Elisa Baker had abused the little girl, prompting cries in the North Carolina community for better protection and reporting of suspected abuse.
"I think there was more behind closed doors than what anybody knew," neighbor Kayla Rotenberry told ABC News. "There was once an incident where Zahra's stepmother was whooping Zahra, and she broke her hand on her prosthetic leg. She said when she was whooping her, she hit that youngin's leg and broke her hand."
The Hickory Record newspaper reported that police there have gotten more than 100 leads from the public and are relying on those tips as well as systematic searches of properties frequented by those who were close to the little girl.
Dogs have been deployed not only in Catawba County, where Hickory is located, but also in nearby Caldwell and Burke counties, the Record reported.
Police have also combed through woods, fields and poured through the family's computers and phone records.
Dogs have found the "presence of human remains" in both of the Bakers' cars, police have said, and "possible blood" was found in one.
ABC News' Yunji de Nies contributed to this story.