The blazes followed other suspicious fires in the area last Monday and Wednesday.
Seven fires were reported along the Tasman Lookout Track in the bush and the dunes last Monday. On Wednesday two bush fires were reported on North Piha Rd, two fires were found on Lion Rock and another on Marine Parade South.
Also on Saturday night, a number of deliberately-lit fires were started on Koraha Road in Kumeu.
A mailbox was lit as were three separate fires along a bamboo hedge.
There was also another fire on a hedge on the corner of Koraha and Old Railway Road.
A police spokeswoman said it was not yet known if the Kumeu fires were related to the Piha fires.
Owner of Adey's Place fish and chip shop Adrian Doggett said he and his wife Vicki were heartbroken.
They were about to board a plane home from Fiji yesterday when they got a call informing them of the fire at their store.
"An innocent little fish and chip shop, victims of sickos. We live in a small beautiful part of the world and these things are quite unusual to say the least but, my God, it affects you when it does."
Doggett told the Herald he had yet to get his head around the financial implications the fire would have.
"We've got all our staff that we've employed that are out of work."
But even in such terrible circumstances the couple remained positive.
"We're philosophical," he said. "We'll be back."
Owner of the Piha General Store and former fire fighter Peter Chapman said frustration and anger were boiling over in the community.
"It's a tight community, Piha, and we want this guy to get caught. When things happen in a small community like this we shoulder arms and stay tight. This is not what our village is about ... For sure we're going to be vigilant and out there with our pitchforks making sure that this person does get caught so we can all sleep at night, particularly our volunteers.
"There's a bit of frustration around. One very good friend's business has been burnt to the ground, we don't want that to happen again. Whether we do that through some vigilante action or however we do it, supporting the police and the authorities, it's a priority for the community."
Detective Inspector John Sutton said the fires were being treated as unexplained and asked residents to be vigilant and report any suspicious behaviour.
"We are aware that there have been a number of reports of suspicious fires in the area this week and are focused on apprehending those responsible.
"Arson is a serious crime and there is potential for an innocent member of the public to be seriously harmed if this continues."
Waitemata's Criminal Investigations Branch is investigating.
