I wonder if there was possibly some kind of evidence in the car(s)...
First, they took the cars...
Next, they said they were investigating family members...
Then, they were searching the landfill...
And now, they have changed to a criminal investigation...
I believe they may have a few of the outside pieces of the puzzle put together, and they are just waiting for someone to get the inside pieces snapped into place...
IMO... The answer to where Sylar is lies within the people at the campsite that night...