actually it shouldn't be. I am sure that I read somewhere (just googled and can't find it now of course) that there is some health regulation that says that they can't leech any toxins if they are cooked etc because people can accidentally cook them (as we see here). I did accidentally microwave one once recently and it didn't seem to cause any damage to the food (but I did get DH to taste it first LOL)

So long as the plastic coating in still intact it should be fine to just keep on cooking it.