AN animal has made a 10 cm hole in a carton, eaten or torn apart a piece of plastic foam packing 20 x 10 x 5 cm and collected a about a kilo of sunflower seeds. No droppings in the carton or around it. The carton was in a garage with open windows.
What sort of intruder have I got?

Sounds like a raccoon to me. I'd set up a live trap with some peanut butter in it to find out for sure.

Could be either a raccoon, a rat, a mouse, a squirrel, all of the above would do the same thing, use the styrofoam for bedding and use the seed for welll umm food,

As said you can get many different sorts of traps, may be the safest bet

Have you been able to find what the culprit is yet?

I suspect a bird! There are never any droppings and I have six window surrounds stored in cardboard boxes. In the top box there is a hole in the side, The styropore packing has been pelletised and there is about a kilo of uneaten sunflower seeds looking like they just came out of the bag.
Here in Stockholm it is winter and our bird feeders are emptied by efficient birds daily. One of them is storing for a hard wintwer.