The Fire Service is still fighting a blaze at the old Southdown freezing works in Penrose.
The fire began at about 6pm on Saturday. It covered the ground, second, third and fourth stories of a derelict cool store.
Acting chief fire officer Wayne Highet told Morning Report on Monday it's still too dangerous for fire-fighters to enter the building, so an investigation into the cause is unable to begin.
He said they could be fighting the blaze for another day or longer.
Pockets of fire cannot be reached because the roof has collapsed in the centre of the building.
Four pumping engines and two aerial fire trucks are still there.
Commuter rail services have now resumed. The railway line alongside the site was earlier closed on Monday morning due to because of debris. Shuttles buses were operating as an alternative service.
Veolia Transport says the line has been cleared and services are now running to schedule.