In my opinion, the police know who took Isabella. The police have a private security company and a surveillance video as witnesses. As seen in the surveillance video, a private security company drove down the alley outside Isabella’s home at 2:36 am. This private company, for some reason, lit up the alley near the Celis’ home with their huge spotlights at 2:36 am. (They must have seen something odd occurring because they don't light up every alley or street.) Twenty-five minutes later (3:00 am), there are people showing interest in the trash bin near the Celis’ home. About an hour before the 911 call, the surveillance video shows a truck speeding around the corner and headed straight for the same trash bin, but what occurs with the trash bin can't be seen.
In the nearly 10 hours of footage, we never see any sign of Isabel. Even though it's from a distance (200 feet), we never see anybody outside her bedroom window either.
http://www.tucsonnewsnow.com/story/31971686/newly-released-video-shows-celis-home-on-night-of-disappearance