He doesn't know why the girl was taken from the hospital but said the amputation might have had something to do with it. He said some of his relatives are assuring him that the girl is fine and getting good medical attention.
Bracamontes said his son sometimes lived in San Jose and sometimes in Phoenix. The family is originally from Mexico.
Phoenix police, meanwhile, say the story of the girl's father raises even more red flags.
"We're in the same spot we were in last Thursday when we began looking for her," police Sgt. Steve Martos said Wednesday. "We understand the right of a parent to change doctors, to change hospitals, we're not challenging that. We just want to make sure that Emily is getting the right medical attention that she requires to prevent this potential horrific ending."
Martos said doctors in Phoenix told authorities that if Emily's catheter is not tended to, it could make her susceptible to a deadly infection that could kill her in a matter of days.
Dr. William Schaffner, an infectious disease specialist at Vanderbilt University Medical Center, said Emily's immune system is already compromised from the cancer and chemotherapy.
"If bacteria get into the blood stream, that can cause a serious infection," Schaffner said.
The open catheter could serve as a pathway for bacteria, he said, adding that a potentially deadly infection is not only possible, but likely.
Martos said the father's story only adds to investigators' bewilderment that began when the mother inexplicably removed the child from the hospital. He said surveillance video shows the mother and child getting into a dark-colored minivan, but the license plates on the car were registered to a different vehicle.
"It all just makes us even more curious that they're unwilling to provide us with basic information to confirm what he is saying, and they're still trying to hide Emily," Martos said. "There's certainly the potential for some criminal charges."
"So we're going to continue looking for her until we either run out of leads or she is found," he added. "We can't just drop it."
Associated Press writer Brady McCombs contributed to this report from Salt Lake City.