Social Services does that. They aren't the evil witches people make them out to be. They usually are very nice. Abrupt and To-The-Point, but nice. And it's always "only for a few weeks till things get sorted out." I think that's a required statement. :)
Foster parents are trained not to ask too many questions at first. And they don't - which I think is a good thing actually. When your placed in a new home, the last thing you want to do is re-tell your whole story to some new stranger.
As to parents explaining? I don't think so. If your child was being removed from your home against your will -- would you be able to calmly and rationally explain to your child that 'It's OK to go with these strangers." I highly doubt that would ever happen. You would kick, scream, and fight the whole time.
