The FBI announced a $25,000 reward for anyone who provides information that leads to an arrest in the case of a missing 11-year old girl in West Stewartstown, N.H.

A private citizen has offered an additional $5,000 reward for information the leads to the return of Celina Cass, who was last seen in her home on Monday evening.

"We are still aggressively, aggressively searching and hoping to bring Celina Cass home," FBI Supervisory Special Agent Kieran Ramsay said in a news conference on Saturday.

Authorities have increasingly intensified efforts to locate Celina since her disappearance, and residents of West Stewartstown -- an 800 person town -- have banded together to assist a frantic search for the schoolgirl, who is described as "shy" and unlikely to have run away.

In addition to the FBI, the Royal Canadian Mounted Police have joined the search effort this week, and on Friday the Connecticut River was lowered to aid in a helicopter search for evidence of Celina's whereabouts.

The home that Celina Cass shares with her mother, sister, and stepfather is a mile from the Canadian border.

Fox News reported that police had cordoned off the home, and Celina's family and the other occupants of the converted apartment building have been relocated while investigators searched phone and computer records.

ABC News obtained court records showing that Celina's stepfather, Wednell Noys, has an arrest record for violating a restraining order and threatening his ex-girlfriend. In 2003, he was forcibly committed to a hospital with a diagnosis of schizophrenia.

CNN affiliate WMUR reported that Celina's mother and stepfather told authorities the girl was gone when they went to wake her up Tuesday morning.

The Boston Herald reported that police officers were seen on Wednesday taking photographs of the interior of a red pickup truck parked across the street from Celina's home. Officers moved official vehicles in front of the pickup truck to obstruct media photographers' attempts to capture images.

 

Celina's mother and stepfather have not made a statement since their daughter disappeared.

Fox News reported that an Amber Alert has not been issued because the circumstances do not meet the state's criteria. "They have to have some specific information they're asking the public to look out for, usually a description of a car, or a license plate number, or something tangible," said Jim Van Dongen, spokesman for the Division of Homeland Security and Emergency Management, who is not directly involved in the case.

"It just doesn't say, 'be on the lookout.' It's got to be something specific."

Officials told ABC News that the disappearance is still being treated as a missing person case.

"Every house, every individual in the neighborhood is being spoken to," New Hampshire Assistant Attorney General Jane Young said Thursday.

Those who knew Cassie believe the girl would not have run away.

"She never went anywhere without her mom or sister,"  family friend Rebecca Goodrum is quoted in the Boston Herald as saying during a candlelight vigil Wednesday night.

"She is very shy," added Kayla Baglio, 18, who also knew the girl.  "If she doesn't know you, she'd look at her sister to see if it was OK to talk to you."

Celina is 5-foot-5 and weighs 95 pounds, with long brown hair and hazel eyes and was last seen wearing a pink shirt, a pink pullover, blue shorts and shoes.

Any information about Celina Cass' whereabouts should be directed to New Hampshire State Police at 603-846-3333.