It was one of four fires that threatened houses in Northland in less than 36 hours, with two homes being destroyed.
Northland police spokeswoman Sarah Kennett said the decision to have an armed officer at the Weaver St house between early yesterday morning and 2.30pm was an operational one based on staff and public safety, but she wouldn't divulge what exact concerns police had.
"This is not a matter that we can comment on at this stage of the investigation," Mrs Kennett said.
She said "an arson scene in its own right wouldn't normally necessitate an armed guard".
Firefighters were called to 3 Weaver St after neighbours saw flames rising from the light green, two-bedroomed house as a man and woman sprinted from the house carrying piles of clothes.
Neighbours told the Northern Advocate they'd heard yelling and watched two people who left the house get picked up by someone in a car at the end of the street, about 50 metres from the house, and the car left "quickly".
Three appliances from Whangarei and one from Kamo attended and managed to have the blaze under control within 30 minutes, but firefighters remained at the house for nearly five hours.
Northland fire safety officer Craig Bain was yesterday investigating the cause of the fire, which he said started at the rear of the fibrolite building. "A whole lot of circumstances point to that it was deliberately lit."
The scene was still under investigation at edition time. Mrs Kennett said, "We are currently following strong leads, which should lead to the people responsible being apprehended."
One Weaver St resident described the fire sounding like a "whole bunch of fireworks going off".
"The whole house had flames coming out of all the windows and doors - it went up really fast."
Thick, black smoke billowed from the house as a boat on blocks under a lean-to also went up in flames, the resident said.
The blaze was one of four fires that threatened homes in Northland in less than 36 hours.
About 4.30pm on Wednesday firefighters were called to a Puhipuhi Rd, Whakapara, home after a small rubbish burn caught long grass and ignited a home. A family lost everything but no one was in the house at the time.
On Wednesday night a small house at Takahue, near Kaitaia, was gutted by fire. Police were also treating that blaze as suspicious and were still investigating there, Mrs Kennett said.
The Kaitaia Fire Brigade was also called out at 2.45am on Thursday to a Parkdale Cres address after a shed at the rear of the property caught ablaze.
The initial fear was that the flames would spread to the house but the fire was contained.
It was believed to have originated from an incinerator that was hard up against one wall.
Mr Bain said dealing with four house fires in less than 36 hours was a lot.
"It's just been all on. It's a case of get some sleep when you can."
Meanwhile, Department of Conservation (DoC) firefighters were yesterday battling a 10-hectare blaze on the border of DoC and Pouto Topu A Trust land at Pouto.
Dargaville Fire Chief Jeffrey Palmer said the fire initially broke out on Wednesday but reignited on Thursday.
"Just the heat of the day is flaring it up and it's hard to put it out," he said.
