Police said a post mortem examination was being carried out today to establish the cause of death.
Detective Inspector Kevin Burke said it was a priority to find who had caused the injuries.
"This appears to be an unprovoked attack on the victim, who was working on his property at the time."
Police said it was believed the assault took place early yesterday.
Mr Burke said police had received a good response from the community.
Anyone with information on Mr Griffin, or any incidents in and around Second Ave between 2pm on Saturday and 8am yesterday, was urged to call Whangarei police.