I actually believe there were probably at least a dozen witnesses that talked to LE about possible sightings of the girls on their bikes that day. We just don't know about them. And that could be for various reasons. IMO, the police are not going to publicly confirm all sightings and they certainly aren't going to tell us every time they receive a tip or lead. They will hold back more info than they will announce to the public. I think that at this point, LE has their suspicions. But without proof, or something more concrete, they will remain silent. They don't want to play their hand and perhaps scare the perp(s) off. I think they want the perp to feel somewhat relaxed because that is when they make a mistake. Over-confidence has been the Achilles heel of many criminals. My friend, and LEO tells me that there is a balance to the info LE releases. LE wants to announce enough to illicit help from John Q Public because it is almost always needed, but they can't announce anything that would give away facts only the killer would know. He also says that, to be sure, the perp is VERY interested in any and all things reported pertaining to this case. It is not uncommon for the police to announce things that aren't exactly true. For example..."we have no leads." Number one priority is finding the perp, while simultaneously working to make sure there isn't a repeat.
My guess is that LE is tailing a few people right now and working from an "unofficial" profile.