About 100 firefighters battled a blaze at a recycling factory at Wingfield in Adelaide's north this morning.
Firefighters were called to the Visy recycling factory on Johansson Road about 3:30am after a smoke alarm was activated and a triple-0 call was made.
At its peak, 23 units from the Metropolitan Fire Service (MFS) and Country Fire Service fought the blaze, which sent smoke over the local area.
The MFS said the fire was expected to burn for several more hours, with bundles of cardboard and plastic fuelling the blaze.
Acting MFS Assistant Chief Officer Eero Harteenan said the origin of the blaze made it difficult to fight.
"We were faced with large fuel loads, limited water access ... compounded by a partial roof colapse," Acting Chief Officer Harteenan said.
"There were several explosions and flames were through the roof.
"The damage bill will be in the millions of dollars."
Authorities were yet to identify a cause of the blaze.
Nearby residents were warned to stay indoors and keep their windows closed until the smoke had cleared.
Johansson Road from the intersection of Cormack and Schumacher Rd is closed and is expected to remain off limits for most of Thursday.
Fire fighters were expected to stay at the site for most of the day to extinguish the fire.
