"In terms of the forensics, unfortunately we weren't able to get any forensics off the box. So it looks like in this case we will be unable to find the offender."
Ms Kalin said the dog was in a frail condition and it was "very much touch and go".
"There has been a little bit of an improvement, but it is still by no way out of the woods.
"Ultimately what will guide our decision is what is in the best interests of the puppy. That's a vet decision, that won't be SPCA organisational decision."
Anyone with information on who may have been responsible should contact Auckland SPCA on 09 256 7300.
"We would really love to be able to identify who was responsible for this heinous act."
Ms Kalin has described the abuse as "absolutely shocking".
"There has been a period of neglect. This is not neglect that occurs over a week, there has been weeks of neglect.
"How someone can look at that dog in the face and not do anything is our greatest concern. The degree of cruelty in this case is one of the worst cases we've seen. And the degree of cruelty cannot go unpunished."
Information on how to make donations to the SPCA to help Bright Eyes can be found here.