WATERVILLE — A 20-month-old girl who was put to bed and vanished a week before Christmas was taken from her father’s home by someone, investigators said Monday as they announced the largest reward ever offered in the state to help find a missing person.

It marked the first time since the search for Ayla Reynolds began that police have directly said they don’t believe she left the house on her own.

“At this point in the investigation … we believe that someone was involved in taking her out of the house, and that’s where the focus of this investigation has turned,” Waterville Police Chief Joseph Massey said at a news conference.

He also announced a $30,000 reward for information leading to the child’s return. The reward is the biggest ever offered in Maine for helping locate a missing person, said Steve McCausland, spokesman for the state Department of Public Safety.

Massey was joined at the news conference by Waterville attorney John Nale. “Through the generosity, support and kindness of a number of individuals and businesses in the area, I offer a $30,000 reward to the person or persons who will provide us with information leading to the location and return of this young girl,” Nale said.

He also appealed for her safe return. “I ask and I plead with the person or persons who have Ayla Reynolds that they please keep her safe and return her safely to us,” he said.

Hundreds of police officers, game wardens and local residents have been searching for Ayla since she was reported missing by her father, Justin DiPietro, on the morning of Dec. 17.

Massey said a report about the case on the Fox network television program “America’s Most Wanted” during the weekend generated some leads, which are being checked by police. He urged anyone with information on her location to contact Waterville police at 680-4700.

The search has now entered its second week. Massey said police are receiving fewer leads in the case, and large-scale ground searches for Ayla ended Friday. Time is a critical factor in missing-persons cases, he said, particularly those involving young children.

“The likelihood of us finding them safe diminishes as time goes on,” he said.

Nonetheless, Massey stressed, investigators are doing everything they can.

“The intensity of the investigation is as high today as it was the first day,” he said. “We continue to employ almost every single resource we have. We’re simply committed to finding Ayla.”

Early Monday morning, investigators returned to 29 Violette Ave. in Waterville, the home where Ayla was last seen. A van from the Maine State Police Evidence Response Team was parked in the driveway and several police cars were parked on the street.

Evidence tape, which had sealed all doors and windows throughout the weekend, was removed from the side door.

DiPietro told investigators he last saw Ayla when he put her to bed the night before at his home. He said she was wearing polka-dot pajamas with the words “Daddy’s Princess” on them and had a cast on her broken left arm. She is 2 feet, 9 inches tall and weighs about 30 pounds.

Ayla ended up with her father after child welfare workers intervened while her mother, Trista Reynolds, checked herself into a 10-day rehabilitation program.

Reynolds, who completed the rehab, had filed court papers that she hoped would lead to the return of her daughter. The filing came the day before Ayla was last seen.

DiPietro has said he has “no idea what happened to Ayla or who is responsible.” He said last week that his family and friends would do “everything we can to assist in this investigation and get Ayla back home.”

– The Associated Press and the Morning Sentinel contributed to this report.