Police are unsure what the motivation is behind the torching of four stolen cars over three days.
The cars were set ablaze in Eastern Beach, Pakuranga, East Tamaki and Otara.
Counties Manukau East area commander Inspector Wendy Spiller says the fires are unusual.
"Usually this kind of incident happens to mask some kind of serious crime, but we haven't been able to link these vehicles to any as yet," she says.
It is not clear whether the four incidents are related.
Kerri, a witness who does not want her last name used, says she and her partner were woken by the sound of a car alarm going off near their Eastern Beach home on Monday morning.
"I went upstairs to see if I could see anything and immediately saw the car in flames in the car park.
"It was an impressive sight, I immediately phoned 111," she says.
The fire crew arrived and dealt with the blaze and police came later that morning.
Kerri says a 5-litre can of petrol was left next to the car.
The gate to the beachside car park, usually closed at 7pm, was left open overnight and the main light was not working.
Counties Manukau police spokeswoman Katherine Manaton says the investigation is in its early days but evidence will be difficult to retrieve.
An Auckland Council spokesperson says a contractor was unable to secure the Eastern Beach car park gate because the lock was damaged or had been tampered with.
A locked gate would not have prevented the car being torched, the spokesperson says.
The council has also organised for the light to be fixed.
The first fire occurred when a car stolen from Onehunga was torched in East Tamaki late on July 11.
Then, in the early hours of July 14, Howick fire crews were called to the Eastern Beach car park at 2.30am and found a car, taken from Chapel Rd, ablaze.
An hour and a half later at 3.50am the crew attended a burning Subaru Impreza on Ti Rakau Dr, Pakuranga.
The car was taken from the same road and torched a few hundred metres away.
The fourth incident occurred late on Monday night on Antrim Cres in Otara when a car that had been missing since early July was torched.
Call police on 261 1300 or Crimestoppers anonymously on 0800 555 111 if you have any information about the fires.
- Eastern Courier