FBI Dogs Search Missing Child's Tucson Home Investigators early Monday sent FBI dogs trained for urban searches into the Tucson home where a 6-year-old girl disappeared as teams of law officers worked to determine if she was abducted. Two days of searching by scores of police and officers from several agencies failed to locate first-grader Isabel Mercedes Celis, who police said was last seen by her family in her bedroom at 11 p.m. When she was discovered missing at 8 a.m. Saturday, they called police. The dogs arrived from the FBI's Virginia headquarters late Sunday and began searching at the home around midnight, said police Sgt. Marco Borboa. "We have deployed the dogs and they're working at the residence," he said Monday. Officers kept the whole neighborhood block where Isabel lives cordoned off for a second day Sunday. More than 150 law enforcement officers were involved in the effort, which included a fourth search of a three-mile radius around the home in temperatures that reached the high-90s, police Lt. Fabian Pacheco said at a Sunday evening news conference. He said the search was being scaled back during the overnight hours, but did not provide any numbers. Investigators found "suspicious circumstances around a possible entry point" at the home police, Sgt. Maria Hawke said. But she wouldn't comment on whether the entry point was a bedroom window or a door. A flyer for missing 6-year-old Isabel Celis is placed on a volunteer's car in Tucson, Ariz., Sunday, April 22, 2012. Police cordoned off a neighborhood block where the girl went missing from her home during the night, as authorities fanned out Sunday over a wide area looking for clues to the possible kidnapping. (AP Photo/Terry Tang) Close Family friend Mary Littlehorn said she heard from others close to the family that a window screen in the girl's bedroom had been knocked down. Earlier Sunday, Tucson police chief Roberto Villasenor said officers had served at least two search warrants. The girl's parents, identified by friends as Becky and Sergio Celis, were helpful as police worked to find their youngest child, he said. He said police were still classifying the case as a "suspicious disappearance/possible abduction." "We're not ruling anything out of the investigation at this point because we really need to keep our mind open about all the information that's been brought to us," Villasenor said. The family has been cooperating with us. Littlehorn, who joined other family friends at a police command post, said authorities separated the two parents for hours Saturday as they questioned them. She said it was difficult for them knowing their little girl was out there somewhere. "She hasn't been allowed to help look for her daughter," Littlehorn said of Becky Celis. Littlehorn has worked with Becky Celis as a registered nurse at Tucson Medical Center for five years. She said Isabel, whose nickname is Isa, loved to play baseball and dance; the girl was supposed to play in a baseball game Saturday. "She's just the sweetest, she is feisty, she's full of life and spirit," Littlehorn said. She said Becky Celis is a registered nurse in the pediatrics unit and Sergio Celis is a dental hygienist. There's no way anyone in the family is involved in the disappearance, she said. "We all feel this is somebody who's been watching 'Isa' for some amount of time to know where her bedroom is," Littlehorn said. Investigators were looking into various scenarios, including the possibility that Isabel wandered out of the home she shares with her parents and two brothers. Hawke said Sunday the wandering off theory was becoming less likely as time passed.