"My hope is that the baby's still alive," police Chief Wayne Brooks said of Joshua Summeries, whose mother reported him missing Wednesday. "My fear is no."
Zion police said in a message posted on the department's Facebook page that more than 50 law enforcement officers and two trained dogs were combing the garbage dump, WMAQ-TV, Chicago, reported.
Brooks said the effort to sort through the landfill debris was "tremendously overwhelming and demanding," the Chicago Tribune reported. Construction equipment was employed in the task.
"We remain steadfast in our mission to find Joshua and more determined than ever to give that small infant a voice in our justice system," Brooks said on Facebook.
No one had been charged in the 5-month-old child's disappearance as of Friday afternoon, the newspaper said.
The mother, who had yet to be named, has told police her boyfriend took her son, the Chicago Tribune reported.
Police interviewed the boyfriend and several other people as persons of interest in the case, Brooks said.
Earlier, Brooks said police worried the boy had been "harmed or worse."
Brooks asked Zion residents to do a "detailed search of their own property and specifically their garbage cans," which he said were "an obvious place to dispose or hide anything of evidentiary value."