An investigation is under way after a house fire grew so big it damaged the living room of a neighbouring home in Wairoa.

Emergency services were called to the “totally involved” fire on Apatu Street about 7pm on Friday.

The house had been vacant for several years, Detective Inspector Marty James, District Manager Criminal Investigations.

A Fire and Emergency NZ spokeswoman said homes in the area, including the neighbours, evacuated as the fire spread.

Four fire trucks and a tanker were called to the scene - from Wairoa, Nuhaka and Manutuke - and a command unit from Gisborne also attended.

Because of the size of the blaze, firefighters were largely tasked with preventing as much damage as possible to the other home, the spokeswoman said.

James said police and Fire and Emergency New Zealand carried out a scene examination on Saturday, though the cause of the fire was unexplained.

“Enquiries are ongoing, but at this stage we are satisfied the fire is not connected to any gang-related incidents that occurred in Wairoa earlier this month.”

On Thursday, Eastern District Police were issued a Gang Conflict Warrant following several incidents stemming from ongoing tensions between Mongrel Mob and Black Power. A significant operation is under way across Hawke’s Bay and Tairāwhiti, including in Wairoa.

The Gang Conflict Warrant is issued under the Criminal Activity Intervention Legislation Act and gives Police special powers to search vehicles of suspected gang members, and to seize firearms, weapons and vehicles, Detective Inspector James said.

“While we do not believe the Apatu Street fire is related to those tensions, Police will continue to have a highly visible presence in the Wairoa community, and in communities around the Eastern District.”