An emergency warning has been downgraded on Thursday night, although authorities warn residents should remain on high alert for changing conditions.
Emergency crews first responded to the fire about 10.15am, which had been burning sulphur and producing large amounts of smoke.
The blaze was contained to the shed but heavy smoke continued to track in a southeast direction, authorities confirmed shortly after 2pm local time.
Fire crews remained at the scene, where they worked to extinguish the fire and manage risks posed by the hazardous materials.
Metropolitan Fire Service Chief Officer Jeff Swann told reporters on Thursday night the fire had been extinguished, but confirmed the cause remained unknown.
About 18 fire trucks, including aerial and hazmat vehicles attended the scene.
"On arrival, firefighters were confronted with a really significant fire involving a large storage shed containing in excess of 30,000 tonnes of sulphur," he said.
"Heavy smoke was issuing from the building and crews immediately commenced firefighting activities, search and rescue and hazardous materials operations."
SA Chief Public Health Officer Nicola Spurrier confirmed one person remained in hospital after being found in a "difficult situation" having succumbed by the time they were found.
Resident Chris Baxter said he was alerted to the fire by his wife, who called him in a panic after hearing word of the evacuation order.
"She was scared, she was panicked," he told ABC radio.
"The warning was to grab your medication and your dogs, or your pets, and go."
Tim Whitrow, who witnessed the blaze from his office, told the radio station that smoke appeared to be coming from the site in thick, white plumes.
Those unable to leave the area were advised to close their windows and doors, and be cautious of smoke.
The fire was contained to the shed and did not spread to surrounding properties, with authorities set to remain at the scene overnight to monitor any hot spots.
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