Jessica disappeared in suburban Denver Oct. 5. The body was found Wednesday in Pattridge Park, about 7 miles from where Jessica was last seen.
Westminster police spokesman Trevor Materasso told reporters Thursday identification was made difficult because the body was not intact.
Westminster Police Chief Lee Birk said Friday investigators are putting all available resources into finding Jessica's killer, The Denver Post reported.
"There is a predator at large in our community," Birk said.
The FBI's Behavioral Analysis Unit has released a profile of some characteristics of a possible kidnapper, most likely a man who suddenly changes his behavior, the Los Angeles Times reported Friday.
"We have no suspects," FBI spokesman Dave Joly said. "We are open to any and all things that the public might find.
"It could be your boss, it could be your friend, and ultimately it could be your family member," Joly said. "Bring this information to law enforcement and let us vet that to a close. If that person is not the suspect, 'Thank you for your call.' Next lead."
Officials said they have ruled out Jessica's parents -- Sarah Ridgeway, who lives in Colorado, and Jeremiah Bryant, who lives in Missouri -- as suspects. They said they have little in the way of clues -- only the discovery of a backpack and water bottle Jessica had with her when she disappeared.
Police said the items were found about 6 miles from where Jessica was last seen.