Is the Associated Press "some random asshole on the internet?" I'm totally using that one!
Here's how I understand the order of events, viewing them as favorably as I can to CPS:
1) Get tip
2) Tip results in some concern
3) Get scared enough to take four police officers to house
4) Ask to inspect
5) Get told "no"
6) Give up
Given the fact that there was no follow up, I think there are only two logical conclusions here: A) CPS (or its NJ equivalent) didn't really believe there was a threat or B) They believed there was a threat, got turned away and gave up.
I can't see any reason to believe anything other than (A).