Read more about this story from CNN affiliate WMUR.
(CNN) -- Authorities in New Hampshire bolstered their search operations Thursday in their search for a 11-year-old who a school nurse described as a "young girl who is afraid and needs to be home."
Speaking on behalf of her community, Kirsten Lyons pleaded for the public's help in locating "our beautiful Celina" Cass, who was last seen Monday night in her northern New Hampshire home.
"Celina is a young girl who is afraid and needs to be home," Lyons told reporters on Thursday. "(She) is missed very much."
About 100 investigators -- including FBI agents, New Hampshire and Vermont state police, local authorities and employees of the state's fish and game department -- went door-to-door Thursday in the small, tight-knit town of West Stewartstown, said FBI Supervisory Special Agent Kieran Ramsey.
New Hampshire Senior Assistant Attorney General Jane Young noted authorities had received about 150 tips as of early Thursday evening, and were checking each one. Help has come from as far as Virginia -- including from FBI headquarters in Quantico -- Pennsylvania and New York, she added.
"It is our greatest hope that we find her and we bring her home safely," Young said Thursday, declining to field questions from reporters.
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.
Authorities have offered few further details on the case, nor has an Amber Alert been issued. Young said that investigators are looking at computer and phone records, trying to find clues.
"I can tell what we have not learned: And that is, where is Celina Cass now?" Ramsey said.
Celina's disappearance has rattled many in West Stewartstown, a town along the border with Vermont and Canada that has about 1,000 people, according to the state of New Hampshire. Friends and relatives have spent much of the past few days putting up posters and doing what they can to find the girl.
"We really want to know that she's OK, that she's safe," family friend Amanda Chapple told CNN Manchester affiliate WMUR. "We want her home. We need her home."
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.
Lyons, who has been a nurse for 15 years at Celina's elementary school, said that the girl "loves her family and is especially devoted to her sister."
"Celina, we want you to know that the entire community -- your friends, your family -- are doing everything possible," Lyons said.