Iris,
Im not sure if its the same for where you live but over here you can send your dead animals to an incinerator. They can give you back the ashes if you want or simply "dispose" of them. Saying that the clinic I work at usually chucks small animals out with the biohazard bag. (oops probably shouldnt have told you guys that!)
As for your dead snakes (sorry to hear about that Khaman
) I would have guessed it as being a heating device malfunction but seeing as I cant carry out a post mortem Im only guessing!!
Hope you find out soon!