Not much HELP, but need some more info. Have you looked in the crawl space and can you actually see the mothballs? Sounds to me like they might have put the mothballs in the crawl to drive out a critter. If they did, you might not want to be in a rush to get them out. Is it possible for a critter to get in the crawl? If they could, find a way to lock them out first. Remember, mothballs don't smell as bad as skunk.
It's also possible that it is something else that is causing the smell. Confirm that it is and let's go from there. Henry in MI