While it may be little more than irrational panic, the markets clearly don't believe the company is telling the whole truth about this incident. Management needs to provide more public information immediately. Of course, it may be a great opportunity for Hecla to buy some cheap shares if such a move is legal or possible.
I am only expressing my personal opinions or repeating public information from SEC filings or media outlets-which may or may not be correct. Do your own investigating before investing!