An Australian woman is under investigation after her in-laws died after consuming a meal she made thats suspected of containing highly poisonous mushrooms, police said.

Erin Patterson, 48, served lunch for her mother- and father-in-law and two of their relatives at her home in Victoria on July 29. Her two children were also present, but they were given a different meal and they, as well as Patterson, did not get sick, police said.

Pattersons husband, whom she is separated from but is said to have an amicable relationship with, was not present, Homicide Squad Detective Inspector Dean Thomas said at a press conference Monday.