( CNN ) -- Investigators searching for a missing 8-month-old boy began an intensive excavation and search effort Tuesday at a Texas landfill . `` Let me say this , that we do remain hopeful that baby Gabriel is alive , '' William McManus , chief of the San Antonio Police Department , said at a news conference at the landfill . `` We are , however , conducting both a missing persons investigation as well as a homicide investigation , '' he said , adding that aspects surrounding Gabriel Johnson 's disappearance involve elements of a possible homicide . Gabriel has been missing since December 26 and was last seen in San Antonio , with his 23-year-old mother , Elizabeth Johnson , who has refused to disclose information on his whereabouts . She told Gabriel 's father she killed the boy and has also said she gave him away to a couple in San Antonio , police say . Johnson drove Gabriel to San Antonio from Tempe , Arizona , and she went to Florida a week later , according to investigators . Johnson was arrested in Florida and extradited to Maricopa County , Arizona , where she remains behind bars , charged with kidnapping , custodial interference and child abuse . A lead prompted investigators to focus on the landfill , which is owned by Republic Services , a waste and environmental services company based in Phoenix , Arizona . The part of the landfill that will be searched has been pinpointed , according to McManus . First , it will take at least six days to remove 45 feet of garbage that has piled up since the time investigators believe evidence may have been dumped in the area . `` Once we have removed the debris and have searched our target area , we will begin the arduous task of sifting through layers in the search for possible evidence , '' McManus said . `` This phase will be a long and repetitive cycle . Search teams will be looking for anything of evidentiary value . '' Cadaver dogs will assist the search teams in the effort , which will be conducted weekdays from 7:30 a.m. to 6 p.m. , McManus said . He estimated more than 20 people will be involved . Rain would not compromise any evidence but could cause dangerous toxic runoff , which Fire Department and hazardous materials experts would work to contain . San Antonio police have been working with the FBI and Tempe police . They have been looking at every lead and `` chasing them down very , very vigorously , '' McManus said . `` We are doing everything that we can to try to track down baby Gabriel , and hopefully we will find that baby alive . ''
8-month - old has been missing since December 26 . His mother has said she found him and also that she gave him away . San Antonio police are searching and in search after finding a lead .