(CNN) -- FBI K-9 dogs hit on items around the southern Arizona home of a missing 6-year-old girl on Monday, prompting authorities to take over the house, a police chief said.
Tucson Police Chief Roberto Villasenor said Monday night that the "specialized K-9s (were) flown in" to help in the case of young Isabel Mercedes Celis, who was reported missing on Saturday morning. The dogs "did alert on some things that caused us to go back" to the house, said the chief.
While they've described her disappearance as suspicious, local authorities have not identified any suspects in Isabel's case nor have they indicated what they believe may have happened to her.
They have launched an extensive search in a 3-mile radius of the girl's home, where she lives with her parents and two older brothers, as well as contacted all registered sex offenders living nearby.
Villasenor said on Monday morning that authorities had combed through the area "at least three times now," with neighbor Cynthia Mort vouching that they'd "searched inside and outside every home in the neighborhood."
The girl's small stature -- at 3 feet, 8 inches tall and weighing 44 pounds -- makes it critical to leave no stone unturned, given that she may be in any number of places.
"We ... are checking every corner, every nook and cranny that could possibly hold a child," Tucson police Sgt. Maria Hawke told CNN's sister network HLN on Monday .
Isabel was last seen by family members when she went to bed at 11 p.m. Friday. When her father went to wake her at 8 a.m. Saturday -- a half-hour after her mother had gone to work -- he said the girl was nowhere to be found, according to police.
A screen was found removed from one of the house's windows. Hawke said the missing screen "could be suspicious" and indicate someone broke through the window to get into the residence or get out, though she stressed "there's nothing conclusive at this point."
Villasenor did not specify what the FBI K-9 dogs hit on, or the possible significance. He did say that, because of their reaction, authorities sought and obtained a search warrant to occupy the house.
He said they asked for a warrant "just to make sure everything is done correctly," not because the family at the center of the case isn't cooperating. Hawke said the family left voluntarily.
"We have asked the family if they would be willing to leave so that we can avoid any potential evidence contamination, ... (and) they have agreed to do so," the police sergeant said.
One street away from one of Tucson's busiest thoroughfares, the Celis' home is in a neighborhood of largely middle-class, single-family residences. A fence and wall surround the yard of the house.
Mort described Isabel's family as "wonderful, caring people."
"They are always helping, you always see them together," said Mort, who has lived next door to Isabel's grandparents for the past 25 years. "They are very, very loving. I couldn't imagine anyone in this family doing anything to anyone."
She added that Isabel's disappearance has rocked the community, leaving "everybody ... totally distraught."
"We're just afraid to let our children out," Mort told HLN. "We're terrorized."