(CNN) -- A central Maine police chief said Friday that authorities now believe there was "foul play" in the disappearance two weeks ago of a 20-month-old girl.
Ayla Reynolds was last seen December 16 when her father, Justin Dipietro, said he put her to bed. Dipietro -- who has insisted that he has "no idea what happened to Ayla" -- later reported the girl missing.
Waterville Police Chief Joseph Massey previously has said authorities were confident that someone took Ayla from the house. But in his comments Friday, issued in a statement, Massey went a step further in saying the case "has evolved from the search for a missing child to a criminal investigation."
Given this shift, the Maine State Police will now take over as the lead in the investigation from Waterville police, according to Massey.
"We base our conclusions on evidence gathered by investigators during the past two weeks," the police chief said.
Maine state police did not respond immediately to a call Friday from CNN seeking comment on their new role in the investigation.
Jessica Reynolds, the missing girl's aunt, told CNN on Friday that authorities said they "can't tell us right now" about what evidence spurred the change, claiming they were told "it isn't done being processed."
"We believed from the beginning that Ayla didn't walk out (of the house) on her own," Reynolds said. "Why it took 14 days for police to say this, I don't understand.
"Time is ticking. The statistics may be that she's not going to come home alive, but, there's also a chance that whoever has her will bring her back safely ... Whoever has her will be found eventually."
Police said Wednesday they had received 370 leads, and Massey said Friday that investigators and searchers had spent "many thousands of hours looking for Ayla (and) evaluating evidence."
A $30,000 reward -- coming from anonymous private citizens and business leaders -- was offered earlier this week for information that leads investigators to the girl.
Ayla is described as having blond hair, being about 2 feet, 9 inches tall, and weighing 30 pounds. She was last seen wearing green pajamas with white polka dots and the words "Daddy's Princess" across the front. When she disappeared, the girl had her arm in a soft cast.
The toddler's mother, Trista Reynolds, told HLN's Nancy Grace that she'd raised Ayla for 18 months and Dipietro became involved after "I needed to go and get a little bit of help for myself." She told HLN she underwent rehab.
The father had sole custody of the girl when she disappeared.
On December 15, the day before Ayla went missing, Reynolds filed a complaint seeking sole custody. The 23-year-old mother told HLN she didn't tell Dipietro she was going to court because he was "vindictive" and "verbally abusive."
For his part, Dipietro, 24, has said he would never do anything to hurt Ayla.
"I have to believe that Ayla is with somebody, and I just want that person to find the courage to do the right thing and find a way to return her safely," the father said in his statement Wednesday. "The truth is the truth and when the case is solved it will be out there. Until then, please try to remain positive and hopeful as I remain confident that Ayla will return safely."
Jessica Reynolds said Friday that she and her sister, Trista, are frantic in their efforts to find Ayla.
"She's extremely intelligent," she said of her niece. "She makes everybody smile when they see a smile on her face."
CNN's Ross Levitt and Susan Candiotti contributed to this report.