(CNN) -- Police in Arizona believe missing 5-year-old Jhessye Shockley was killed and think they know where her body was placed.
Information from leads, including a "silent witness," led authorities to believe the little girl's body was dumped in the trash and ended up in a landfill, Glendale police said.
But authorities said there are no immediate plans to search the landfill. A decision on whether to conduct a search "will be finalized in the coming weeks," police said in a news release.
"This is an active homicide investigation," the police department said.
The girl's mother, Jerice Hunter, remains "our primary focus," Glendale Police Department spokeswoman Tracey Breeden told CNN.
Information gathered from leads and tips and through investigating "lead us to believe that she was involved," Breeden said.
Asked why Hunter has not been arrested, Breeden said police "have one shot at this" and "have to be precise and methodical."
"We're getting closer to solving the case," she said.
The mother's attorney, Scott Maasen, told CNN Thursday that Hunter "certainly declares her innocence."
Hunter has said her daughter wandered out of the family's Glendale home on October 11, unnoticed by her 13-, 9- and 6-year-old siblings, who were supposed to be watching her.
Maasen said the children were playing in the backyard behind their apartment complex when Hunter went to the store. When she came back, she found that her daughter was missing, Maasen said.
"She's been steadfast in every conversation we've had," he said. "She wants to find Jhessye, wants to know where her daughter is."
Hunter was arrested in November for alleged child abuse, then released a week later. Police said she was suspected of having abused Jhessye based on reports from the child's siblings.
When they released Hunter, police said prosecutors had decided not to charge her "at this time."
In a statement Wednesday, police said that shortly after that arrest, "investigators received reliable information from leads. Based on this information, and further investigation, we believe Jhessye Shockley's body was placed in a trash receptacle located in the city of Tempe prior to the report of Jhessye's disappearance on October 11."
Trash from the location is taken to a transfer station and ultimately to Butterfield Landfill, police said.
Over the past few weeks, investigators have been "determining the viability of a landfill search at that location," the news release said. "That includes conducting analysis to determine the likelihood of success of recovering Jhessye's body. The decision whether to search will be finalized in the coming weeks."
Asked by CNN who may have put the body in the trash, Breeden said only that it is "good, reliable information that came from a silent witness," and the information came to light during the time that Hunter was under arrest.
Police said they determined Wednesday that it would not compromise the investigation to release the new information.
The news release added that Hunter "has not submitted to a polygraph, but our investigators encourage her assistance and cooperation in this investigation and would certainly make a polygraph examination available through her attorney."
Maasen, her attorney, told CNN polygraph tests are "not reliable," but nevertheless, "it's something we'll consider."
He accused authorities of "stonewalling," failing to share information with Hunter. "I'd like to see the witness statements, police reports," and other information, he said, adding that if there were more cooperation, his client might agree to a polygraph.