I would not go talk to the neighbors about it! That will only make you a target, if it's drugs. The most important thing is for you to be safe. Besides, what are they going to tell you if it is drugs? The truth? You won't know any more after you talk to them then you do now, you'll just be exposed. Then you won't be able to safely call the police. As was pointed out, meth labs exploding is a real concern if it's near your house, in addition to other concerns about it.
If it happens again and you call the police, it should be fairly easy for them to figure out what's going on. They should have plenty of experience at this. If there's nothing bad going on over there, it won't be any more of a problem for the neighbors than if they had their music too loud or had a dog barking too much and the police stopped by.