CYRIL, Okla. (KFOR) – The desperate effort to find a little girl missing from Cyril continues as investigators work to find four-year-old Athena Brownfield, who hasn’t been seen since at least Tuesday.

The investigation into the disappearance for Athena started after a mail carrier found her five-year-old sister outside of their home, alone on Tuesday.

Hundreds gathered to scour the town in an exhaustive searched that spanned late Tuesday and all-day Wednesday.

But so far, the search has led to more questions and answers, including where the girls parents are and exactly how long she has been missing for.

OSBI told KFOR those details are part of the investigation but did not offer any more immediate details.

“We’re still building that timeline [of her disappearance], and we’re talking to witnesses and neighbors and people in town,” said Brook Arbeitman, OSBI.

“What I can confirm to you, that is not rumor or innuendo, is this investigation began at two o’clock yesterday when her five-year-old sister was located by the postal carrier,” she continued.

“We are collecting items that could be relevant. I’m not going to call them evidence, but we are finding things around town that could be helpful in this case.”

KFOR also learned Wednesday that Athena’s sister is currently in protective custody.

“[I feel] heart wrenching chest pains [and] sick to my stomach,” said Penny Brownfield, who identified herself Wednesday as Athena’s grandmother, telling reporters that the family is trying to stay “hopeful and positive” throughout the ordeal.

“We just want her found and safe,” she added.

The ongoing grid-by-grid ground search was called off Wednesday afternoon as federal agencies move their search outside of the town, saying they’re confident they’ve searched every square inch.

While authorities said the day’s exhaustive search was fruitful, they’re shifting their focus outside of Cyril.

“We had with the purpose to search the entire town. And that has been completed,” said Trooper Eric Foster of the Oklahoma Highway Patrol.

“[Now] there are other resources being utilized to continue to search for her,” he added.

“This is really a search for this little girl. and we will continue to do until we have to move to another step.”

OSBI is now leading the investigation with the help of several other agencies, including local law enforcement, the Comanche Nation, Fort Sill and the National Center for Missing and Exploited Children.