The frightening incident happened in Maraenui. Photo / Paul Taylor
A police spokeswoman said pepper spray was permitted to be used by an officer "to deter an attacking animal" as part of police protocol.
A witness at the scene, who did not want to be named, said the actions from police may well have prevented a further attack.
The witness said one officer was holding what appeared to be a Taser but did not use it, while the other officer used pepper spray on the white dog.
Napier City Council animal control were called by police and seized the white dog.
"The incident is currently being investigated and the dog will be held until the investigation has been completed and a decision has been made as to what action we will take," a Napier City Council spokeswoman said.