Food Standards Australia and New Zealand is working with relevant food businesses and state food authorities to coordinate the national recall.
"Consumers who have the batch of spinach in question should not eat it and dispose of it," the agency said in a statement on Friday.
Authorities believe the product, Riviera Farms-branded baby spinach, might have been accidentally contaminated, leading to people experiencing possible toxic reactions including hallucinations and delirium.
The national recall includes bags of spinach sold through Costco in NSW, Victoria and the ACT with use-by dates from 16 December up to and including 28 December.
Authorities have warned the product is not safe to consume and people who still have it stored at home should throw it out.
NSW Health said it was working with other jurisdictions to investigate the issue and by Friday evening 47 people had reported symptoms after eating baby spinach, at least 17 of whom had sought medical help.
In a statement, Riviera Farms said it had issued a recall of all its baby spinach products with best-before dates up to and including 28 December as a precautionary measure.
"It appears these products, which were grown on a farm in Victoria and shipped to stores in NSW, have been contaminated with a weed which can have health consequences if consumed," it said.
The company said it would continue to work closely with health and food regulators as investigations continue.
"Riviera Farms has been in the business of providing fresh food since the 1880s and we are saddened to confirm that we have likely had our first ever significant contamination incident," it said.
Customers concerned about exposure to the spinach should call the Poisons Information Centre, while anyone who experiences unusual and severe symptoms should seek immediate medical attention.
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