Suppose a Mashgiach realizes that a store is selling Treif meat, however is unsure as to the source of the problem. If he announces immediately that this store is selling something not Kosher he may not be able to catch the one who is supplying the not Kosher product and thus it may continue elsewhere. Would the Mashgiach be allowed to wait, and cause those who use this store to continue to eat not Kosher, in order to catch the bigger fish and thus eliminate the problem completely or he would have to announce immediately his findings? (sources please)
Rabbi Yitchok Zilberstain brings down from Rav Elyashiv Zatzal that you should immediately let everyone know.