The B.C. SPCA alleges that the Greater Vancouver Zoo is withholding details about the third death of a giraffe at the facility in the past year.
Investigators were at the zoo on Wednesday to look into the weekend death of 12-year-old giraffe Jafari, but zoo officials are withholding information, SPCA spokeswoman Lori Chortyk claimed.
Chortyk said a search warrant might be necessary.
"We have run into some situations where they are not being entirely co-operative and we're now having to take some legal steps to get the information we need for an investigation," said Chortyk.
None of the SPCA's allegations has been proven.
Two other giraffes died within a week of each other in November 2011. Now only one giraffe, named Pompy, remains.
Preliminary necropsy results showed that because Jafari apparently had ample stores of body fat, cold weather did not kill her, said spokeswoman Jody Henderson.
"They thought there might an infection in his intestines and that [theory] is in the very early stages."
Jafari had been at the zoo since 2001.