Mushroom experts from Melbourne’s Royal Botanic Gardens have reportedly been called in to help identify the fatal ingredient suspected to have been in a lunch that killed three people.

The Herald Sun reports at least two mycologists are working with Victoria Police’s homicide squad to confirm which type of mushroom, if any, was in the fatal last meal.

The mushroom experts will help identify what toxin was present in the beef Wellington, which could involve examining fragments of any leftovers, or using samples from the survivor, Baptist church pastor Ian Wilkinson.

Police have stated they believe poisonous death cap mushrooms were in the food served by Erin Patterson to her four guests, three of whom later died, with one still in hospital.

A month after the deadly meal, police are still investigating the mysterious circumstances that killed couple Gail and Don Patterson, both aged 70, and Mrs Patterson’s sister Heather Wilkinson, 66.

Detectives consider the Pattersons’ daughter-in-law Erin Patterson a suspect as she cooked the lunch that is believed to have led to the deaths.

In a statement to police, Ms Patterson claimed she made a beef Wellington using button mushrooms from a major supermarket and dried mushrooms bought at an Asian grocery store.

But Australian mushroom growers have been seeking to reassure the public that commercially bought mushrooms are safe to eat.

The Australian Mushroom Growers Association said it was impossible for death cap mushrooms and other dangerous varieties to be grown in commercial operations.

“This fungus (death caps) only grow in the wild,” the association said in a statement.

“Commercial mushrooms are grown indoors in environmentally controlled rooms with strict hygiene protocols and food safety standards.

“The only mushrooms you can be sure are safe are fresh, Australian-grown mushrooms bought from a trusted retailer.”

The Victorian health department is required to act if there is a food safety incident.

There have been no ordered recalls of mushroom products in the state since the suspected poisonings.

-with AAP