Police said Monday that they’re “not closing the door” on any possible explanations for the disappearance of six-year-old Isabel Mercedes Celis from her Tucson, Arizona, home.

Tucson Police Chief Roberto Villasenor told reporters authorities have not made any determinations about what they have described as a “suspicious disappearance and possible abduction.” Isabel’s parents reported her missing Saturday morning, telling police that she vanished from her room in the middle of the night, according to a police press release.

Villasenor said on CNN Monday that an open window was found in Isabel’s bedroom with the screen removed, so that is being looked at as a possible point of entry. The girl was last seen when she was put to bed around 11:00 p.m. on Friday, and she was gone when a family member went to wake her around 8:00 a.m.

At a press conference Monday, Villasenor said investigators have been going door to door searching homes in the neighborhood while they continue to process the family’s house for forensic evidence. FBI K-9 handlers with trained dogs have been assisting with the search effort at the house and police are following up on what they have found.

According to Villasenor, Isabel’s parents have been cooperative and investigators know where they are if they need to speak to them again. He called them the “best source of information” for finding their daughter, although he told ABC News earlier in the day that nobody, including the parents, has been ruled out as a possible suspect in the case.

Isabel Celis is described as 44 inches tall, approximately 44 pounds, with light brown hair and hazel eyes. Her hair was braided when she was last seen and she is missing two of her front teeth. Anyone with information regarding her whereabouts is asked to call 520-882-7463.

For the latest on Isabel Celis’ disappearance, watch Nancy Grace Monday at 8 p.m. and 10 p.m. ET on HLN.

TUCSON – Tucson Police say more than 500 tips have come in regarding the disappearance of Isabel Celis. One hundred of those tips were reported between Tuesday and Wednesday afternoon. The six-year-old was reported missing from her east side home 12 days ago.

On Wednesday, detectives entered the Celis home with the girl’s father, mother, and two brothers. The family has control of the home and investigators were there with the family’s consent. Lt. Fabian Pacheco from the Tucson Police Department said the visit was a routine part of the investigation.

“They’re escorting family in and out, speaking with them independently. It’s just a continuation of their work. I can’t talk with you about specifics that they’re dealing with or questions that they’re asking it’s just furthering their investigation,” Lt. Pacheco said. According to Pacheco, detectives have not focused on one particular scenario or person, “It’s part of the continuing investigation and just the method that detectives do their work,” he said. Pacheco also told reporters at Wednesday’s press conference that detectives had been working with state police in Sonora. At least five tips have come with reported sightings of Isabel south of the border. Pacheco said the girl was spotted in Magdalena, which is south of Nogales, but the information did not turn up any significant results. He said investigators had not been to Mexico since the investigation began.

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