The dog that bit a Hamilton woman's neck and face was already known to local authorities because of its behaviour.
The woman was bitten by the mastiff cross at a property in Avalon Drive just before 3pm yesterday.
She remains in Waikato Hospital.
Hamilton City Council said the dog is just under six years old and has been owned by the victim since it was a puppy.
It says the dog was given a 'menacing' classification in 2010 after an incident involving another dog, but said it has received no other reports about the dog since then.
The dog has been seized.