Rabbi Ya'akov Ariel, the chief rabbi of Ramat Gan, called on people, Friday, only to buy leavened products from stores with certificates showing that they sold their chametz to non-Jews to the letter of the law before the recent Passover holiday. Interviewed by Arutz Sheva's Hebrew service, he said, "There are stores that sell chametz but Jews actually kept Jews buying chometz there on Pesach, cancelling the sale retroactively and no benefit may be derived from the chametz. That is why many Jews are careful to not buy chametz until a month after Passover, when there has been a new cycle of chametz products on the shelves."
Rabbi Ariel said his warning applies to completely chametz product, including wafers, noodles and other pasta. It does not apply to products containing minute amounts of chametz.