Updated

Police began excavating a landfill Tuesday in search of a body or other evidence in the disappearance of an 8-month-old Arizona boy who was last seen with his mother at a San Antonio hotel on the day after Christmas.

Elizabeth Johnson, 23, was locked in a custody dispute with the baby's father when she took off from Tempe, Ariz., in mid-December. Johnson has refused to say where the baby is, but she told the father, Logan McQueary, that she killed the infant and threw his body in a trash bin — a story she later retracted in a media interview.

Police Chief William McManus said Tuesday that authorities began the arduous task of digging down through 45 feet of trash with hazardous material crews and cadaver dogs standing by. It will take at least six days to dig to the layer containing trash from the hotel. The hotel's trash, which is in a section that's been cordoned off for weeks, will be recovered and carefully sifted, he said.

"We do remain hopeful that Baby Gabriel is alive," McManus said at news conference near the landfill's edge. "We are, however, conducting a missing person investigation and a homicide investigation."

He declined to offer any details on the investigation, which began as a missing-person case but was reclassified as a homicide to allow for the landfill dig. McManus said leads have come in from a variety of sources and investigators are checking every one.

Safely conducting a landfill search requires careful planning and specially trained investigators, McManus said. Heavy rains, which create toxic run-off, also have been a concern, he said.

Johnson, who was arrested in Fort Lauderdale, Fla., on Dec. 30, is jailed in Arizona on charges of kidnapping, child abuse and custodial interference.

She told Phoenix television station KPHO that she gave the baby to a couple in a San Antonio park and only said she killed the boy to get back at McQueary, who had refused to give the baby up for adoption. Investigators say her descriptions of the purported hand-off were vague.

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