Firefighters say lives are being put at risk after a second fire was believed to have been deliberately lit at an unused power station in Ruakākā.
Emergency services were called to Sime Rd, off Marsden Point Rd, at about 11pm on Wednesday after receiving reports of a vegetation fire.
Ruakākā chief fire officer Warren Marshall said the blaze was around 50m by 50m and took more than two and a half hours to put out with the help of two tankers and four fire trucks.
He said the fire had clearly not been caused by a natural event. Police are appealing for information about the fire.
The location of the fire could have made it far more serious as Niwa and the new power station are nearby and the site is difficult to access, Marshall said.