The body of the girl, missing since Monday, was found in a nearby pond on Thursday afternoon in the eastern German city. Shortly thereafter it was determined she had been murdered.
Police late on Thursday announced the girl's death had not been accidental, but refused to release other details while the search for her killer moved into high gear.
"We don't want to tip off the perpetrator while he's still running free," chief prosecutor Hans Strobl said at a press conference.
Police in the German state of Saxony received a tip led them to find a girl's body in a pond earlier this week. State police chief Bernd Merbitz said on Thursday it was the girl named Michelle.
Michelle's parents reported her missing on Monday evening after she didn't come home from playing. Police launched a massive search on Tuesday that included dogs, helicopters and some 150 officers.
Police are also investigating witness reports from one of the girl's friends, who reported that Michelle had said she was going to see “L.” It remains unclear what or who “L” was, police said.