A fire that gutted a Four Square supermarket north of Auckland overnight is being investigated to see if it was deliberately lit.
The scene has been guarded since up to 70 firefighters battled the blaze at Warkworth last night.
Fire service shift manager Steve Smith said 15 trucks were flanked by support units in containing the fire, which was reported about 7.40pm.
"We've had a scene guard overnight so they're obviously looking for something in particular," Mr Smith said.
The fire was extinguished shortly before midnight.
Fire investigators will be on scene this morning to look for what caused the blaze.
