I Accidentally Put A Plastic Lid Over A Casserole Dish

I accidentally put a plastic lid over a casserole dish and heated it up in the oven. After an hour being in the oven I took the dish out only to find the lid had melted around the dish. I pulled the lid back and it didn't look as if the lid touched the food. Is the food okay to heat or would it be too toxic to consume? Oddly enough, I didn't smell the plastic when it was in the oven.