Christchurch Police have released CCTV images of the Garlands Rd fire suspects.
The 40-second video shows four people, one holding a cell phone with the torch on, walking around the yard near a container.
The fire raged after scores of cars erupted at a scrap metal yard in Woolston, Christchurch, sending flames shooting at least four storeys high into the air.
Fire and Emergency NZ contained the fire to the main car pile that burnt for some time given it was deep-seated.
Detective Sergeant Michael Varnam said police hope someone will recognise those involved, particularly people who know them.
"This incident was extremely serious, and had it not been for the fast work of FENZ, could have caused considerable damage to homes and businesses, as well as serious risk to people's lives.
"We also are asking anyone who has CCTV cameras in the area and thinks they may have relevant footage to contact police."
Police have been investigating since the large blaze at Garlands Rd on the evening of August 17.
It took a number of days and significant work by FENZ to get under control.
A witness at the scene told the Herald the flames were "at least four storeys high" and the fire "seemed to be growing rapidly" as cars burst into flames.
"There are loud snaps and bangs coming from the cars and there are sparks going everywhere."
The CCTV footage shows four people in the area at the time of the blaze.
Police said they know the footage is not very clear but have released it in the hope of identifying the four people.
If you know anything contact police on 105 phone service or online at https://www.police.govt.nz/use-105, using Update My Report, and reference file number 220822/8276.
Alternatively, information can be provided anonymously via Crime Stoppers on 0800 555 111.