PHOENIX (Reuters) - Police are looking for an 11-year-old leukemia patient spirited out of a Phoenix hospital by her mother and are concerned a chest catheter in the girl's heart could lead to a fatal infection, authorities said on Tuesday.

Emily Bracamontes went missing from Phoenix Children's Hospital on November 28, said Phoenix police spokesman Sergeant Steve Martos.

The girl, who has leukemia, had previously been brought into the hospital by her mother for treatment, Martos said. During the treatment, a chest catheter was inserted into her heart.

Martos said that "for unknown reasons," the girl's mother, Norma Bracamontes, 35, removed the IV feed from her daughter's catheter, changed the child's clothing and sneaked her out of the hospital.

"We have been informed by medical personnel if the catheter is not medically removed, the victim's heart could potentially become infected resulting in the child's death," Martos said.

Emily previously had her right arm amputated due to infection, police said.

"(We) have worked tirelessly in an attempt to locate Emily and her family to ensure she receives the proper medical treatment she requires," Martos said.

He said it was too early to determine if Emily's mother would face criminal charges.

On Saturday, the U.S. Border Patrol stopped and questioned the girl's father, Luis Bracamontes, 46, as he was entering into Arizona from Mexico.

Police said he denied involvement in the incident or knowledge of his daughter's removal from the hospital and had no information on the whereabouts of Emily or her mother.

Luis Bracamontes was not in the Ford mini-van last seen leaving the hospital when Emily was removed from the facility, police said.

In an effort to find Emily, police have released surveillance video of the girl and her mother walking through the hospital as they were leaving.

Jane Walton, a spokeswoman for Phoenix Children's Hospital, declined to comment on the case, citing patient privacy rules.