The two main Satanic organizations, the Church of Satan and the Temple of Seth, both strictly forbid animal sacrifices and the use of animal parts in their rituals. As far as I am aware even quite a few British home-grown cults do so, although it's not possible to say if this is done out of belief or to draw as little attention as possible.
As far as Pagans are concerned a few sects have been suspected of practicing animal sacrifice in the past and Odinists are known to "sacrifice" to their Gods supermarket-purchased meat, though this is almost invariably incinerated or consumed in a ritualistic feast and not left laying around. They tend to favour lamb.
I can assure you that traditional Wiccans would have nothing to do with using animal parts in their rituals, let alone willingly harm an animal. They are quite a bit touchy on the subject...
Caribbean and Latin American religions originated from African belief systems (Santeria, Palo Mayombe, Candoblé etc) are known to make vast use of both colored candles and animal sacrifice, though the latter almost invariably involve a chicken or, if circustances allow, a goat.
The problem is there litterally hundreds of dabblers in the occult and "weekend satanists" out there, those beliefs and methods cannot be fathomed and tend to be quite crude and unpleasant, ranging from writing 666 on a wall with spray paint to graveyard desacration. Also do not rule out pranksters.
In my opinion the culprits are to be found in these latter categories.
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Fas: Ite, Maledicti, In Ignem Aeternum.