A couple of things:
1. I thought I heard Superintendent Doug Carter mention "the largest pedophile ring in Indiana's history" in one of his press conferences. He didn't amplify that statement. It was a one-line statement buried in a press conference about the Delphi murders. It would be easily lost or overlooked in the flow of the conference. When the previously mentioned participation of the Federal Marshals is considered, with their participation in countering child trafficking crimes, those two things might point toward a more developed and wide-spread investigation about other crimes and criminal relationships that developed progressively from the initial murder investigation. (Carter's comment might have been stock footage from another, non-Delphi press conference, where a television station does a news cast on the Delphi case, but used a quick image and statement from a separate news conference. It can happen in broadcasting when a representative image is used, and not always one from the immediate time or thing being discussed. I'm not sure on this point.)
2. County and state-level investigations can become quite lengthy, involved, and complex multi-jurisdictional affairs. A sustained surveillance of a significant suspect is not beyond the possible technical or resource capacity of modern law enforcement, especially if it is passive technical surveillance (not people intensive). Some counter-drug task force organizations reflect this, because the drug trafficking network might span multiple counties.