In a case of an accidental contamination of a batch of spinach sold in Australia, dozens of people have become sick, with some experiencing hallucinations.

"The patients that have been quite unwell have been to the point of marked hallucinations where they are seeing things that aren't there," New South Wales (NSW) Poisons Information Center medical director Dr. Darren Roberts was quoted by the Sydney Morning Herald. "They can't give a good recount of what happened."

"No one has died, so we're very happy with that, and we hope it remains that way, but these people are quite sick," Roberts added.

Riviera Farms baby spinach bought at Costco is believed to be the culprit behind severe food poisoning observed in people.

"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," Riviera Farms said in a statement.

"Early reports are that our one-kilogram plastic tubs of spinach with a best-before date of December 16 may be contaminated with a weed which can have health consequences if consumed," a spokesman for Riviera Farms said, the Sydney Morning Herald reported.

The contaminated spinach affected 47 people in NSW, who reported symptoms after eating the spinach, and at least 17 people needed medical attention, according to the state's health department.

The New South Wales Health authority warned of adverse symptoms from consuming contaminated spinach, including delirium or confusion, hallucinations, rapid heartbeat, and blurred vision, according to ScienceAlert.

Investigations are underway to find and pinpoint the exact cause of contamination in spinach.

"There are many possible causes for this – overseas we can see another plant accidentally entering supply," Roberts said. "Lots of tests are being conducted based on material that's left and the blood and urine of patients [but] we feel pretty confident with the type of chemical that's caused it."

The spokesman for Riviera Farms assured the public when the company was alerted of possible contamination by one of the retailers it took swift action and "immediately advised them to remove our impacted spinach from their shelves and contacted state health and federal food authorities."

People were found to be sick even after 24 hours from symptom onset, Roberts said.

"When people have these kinds of symptoms they should go to hospital, these effects won't go away on their own," Roberts advised.

Pictured: Representative image of spinach. Thilo Becker/Pixabay