Police are urging early risers in the Whangārei suburb of Tikipunga to be extra vigilant after two more arson attacks on parked cars this week.
Whangārei police are now investigating five car fires this month alone, with one on Monday and another on Wednesday morning.
Monday's fire started about 5.30am on Meadow Park Crescent while Wednesday's was on Paramount Parade about 5am.
Detective Sergeant Pieter Serfontein said all the fires had started before dawn.
"I'm asking those that live in Tikipunga, or those passing through, to be extra vigilant around this time period," he said.
"We need to hear straight away if you see suspicious activity taking place. Whether you're walking the dog, going for a walk or heading off to work - we need to hear from you."
Any people or vehicles acting suspiciously should be reported by calling 111.
Serfontein said a second vehicle was targeted on the Paramount Parade property on Wednesday morning but that arson attempt was unsuccessful.
Anyone with information about the person, or people, responsible should call 105, quoting reference number 240912/0211.
Information can also be provided anonymously via Crime Stoppers on 0800 555 111.
Another car fire on a driveway in Tikipunga earlier this year spread to a house and caused the death of 61-year-old John Reuben, also known as Hoani Reupena-Tuoro.
A 48-year-old Whangārei man, August Lemon, was arrested last month in relation to that fire and charged with knowingly endangering life by setting fire to property.
He has denied the charge and is in custody awaiting his next court appearance.