Yes - The very first statements from LE indicated that there was some level of cooperation. For ex., in the press conference on June 7, they said they had talked to people who were with her on thursday night/ friday morning and mentioned searching apartments and cars (not specific about whose). It's not clear how voluntary that cooperation was, at least for any searches, since I would assume LE would be certain to get warrants to make sure there would not be problems later on, in case of a trial. The search that was reported by media (where CR, JR and JW's places were searched with dogs) didn't happen until almost a month later though - I want to say June 30th? I've never understood why it took place so late.
By that point, though, LE and the Spierers were clear that they were not getting full cooperation from the POI. IIRC, they had left town, refused to take LE polygraphs and the guys at 5 N wouldn't talk to the Spierers. At the press conference on June 24, the Spierers were pleading for help and information and Capt. Qualters made that statement about the 'perplexing' behavior of Lauren's friends. He also made a statement (not quoted in this article) about not being able to compel people to come in and speak with LE, especially if they are out of state (JR had left Bloomington as early as a few days after Lauren's disappearance, and soon after, JW, CR and MB - this info is in that article I posted upthread about CR's drug charges).
http://abcnews.go.com/US/lauren-spi...friends-search/story?id=13923810#.T8ast1KD840
[The links about the early searches and press conferences can be found in the media thread]