PHOENIX — The mystery surrounding the whereabouts of a sick girl with leukemia deepened Wednesday after her father said his 11-year-old daughter is being treated in Mexico and authorities considered bringing child neglect charges against the family.

Phoenix police have been looking for Emily since surveillance video one week ago showed the girl’s mother walking her out of Phoenix Children’s Hospital a day before the child was set to be released. Doctors say she could contract a potentially deadly infection if not returned for treatment. Phoenix police said the parents could face criminal neglect charges if they didn’t return the girl.

The girl underwent about a month of chemotherapy and had been treated for an infection that forced doctors to amputate her arm, police said.