A weed at the centre of a nationwide spinach recall has been identified.
Riviera Farms says thornapple, also known as jimsonweed or Datura stramonium, became mixed in with its crop.
Melbourne University botanist and associate professor Andrew Drinnan said the datura genus was part of the solanaceae or nightshades family of flowering plants.
"That's the family that tomatoes and potatoes are in, and tobacco and capsicums and eggplants," he told AAP.
"A lot of them are well known for having toxic alkaloids. They are to stop things from eating them."
Almost 200 people have reported symptoms such as vomiting and hallucinations after eating the contaminated spinach in recent weeks, including a child in Queensland who was admitted to hospital.
The weed is an invasive species believed to originate from Central America that arrived in Australia in the early 19th century.
Costco, Woolworths, Coles and Aldi have stripped Riviera Farm's products from their shelves and a recall has been issued.
"The investigations have not identified any other potential chemical, herbicide or other type of contaminant," a spokesperson for Riviera Farms said in a statement.
No other produce from the farm has been impacted, but nearby crops will be destroyed as a precaution.
Experts from VicHealth helped to identify the weed, which is poisonous to animals and people, particularly children.
Datura stramonium seeds are commonly used in ayurvedic medicine for their analgesic, anthelmintic and anti-inflammatory properties.
This week, peak industry body AUSVEG urged Australians to keep supporting vegetable growers, saying the recall was limited to spinach from a single farm in Victoria.
Australians who consumed the products were told to watch out for symptoms including delirium or confusion, hallucinations, dilated pupils, rapid heartbeat, flushed face, blurred vision and dry mouth or skin.
People who experience any of the symptoms should seek medical attention immediately.
The affected products are:
* Riviera Farms branded baby spinach
* Fresh Salad Co Fresh and Fast Stir Fry
* Woolworths Chicken Cobb Salad and Woolworths Chickpea Falafel Salad
* Coles Spinach 60g, 120g, 280g
* Coles Chef Blend Tender Leaf 150g
* Coles Baby Leaf Blend 300g
* Coles Kitchen Green Goddess Salad 250g, 300g
* Coles Kitchen Roast Pumpkin, Fetta and Walnut Salad 265g
* Coles Kitchen Chicken BLT Salad Bowl 240g
* Coles Kitchen Smokey Mexican Salad 280g
* Coles Kitchens Egg And Spinach Pots 100g
