Yes they can. We did this every time we had them left over in the high school cafeteria I worked at for 6 years. Now I have never done it at home which would be no different. At school we just put them single layer and then waxed paper, another layer of squares and another layer of waxed paper, then completely covered tray and all with plastic wrap, then foil. We didn't use them again until the next month and they tasted fine once they were thawed.
this site says you can.
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