(CNN) -- The father of a missing 11-year-old girl New Hampshire girl pleaded for her safe return Sunday, six days after she was last seen in her home.
Local, state and federal investigators continue to look for Celina Cass, with searches being conducted "by air, by land, by water" in and around the girl's hometown of West Stewartstown, New Hampshire Senior Assistant Attorney General Jane Young said Sunday.
She noted that authorities, which include FBI members, had received more than 400 leads as of early Sunday evening but, "at this point, we still have not discovered Celina." The community of about 1,000 people borders Vermont, and is also very close to the Canadian border.
"We are working tirelessly to bring her home," Young said.
The girl's father, Adam Laro, said Sunday that he's recovering after being recently released from the hospital -- sending a message to his girl that "Daddy is OK now, I'm getting much better." He did not detail why he had been hospitalized.
He added that he, like others, is "wondering where my daughter is" and hoping she is safe.
"Whenever you want to come home, Celina, Daddy will be here waiting for you," Laro said.
Celina was last seen in her room, at her computer, at about 9 p.m. Monday night, according to police. WMUR reported that her parents told authorities the girl was gone when they went to wake her up Tuesday morning.
Friends have set up a Facebook page, "Missing Celina Cass," with one of the fliers serving as a profile picture. According to the flier, Celina is 5 feet, 5 inches tall and weighs 95 pounds, with long brown hair and brown eyes. She was last seen wearing a pink shirt, pink pullover and blue shorts.
Young said Sunday that investigators consider this a "missing persons" case. Authorities have offered few further details on the case, and an Amber Alert has not been issued. Among other pieces of potential evidence, Young has said investigators are looking at computer and phone records, trying to find clues.