Updated

Authorities say the toxic mushrooms that killed two residents of a California senior care facility and sickened four others came from the home's backyard.

Placer County sheriff's investigators said Tuesday that the caretaker who picked the mushrooms and prepared soup for the home's six residents had no idea they were toxic.

The caretaker was among the four who fell ill Thursday after eating the soup at Gold Age Villa in Loomis. Investigators say the poisonings were quickly traced to the soup because the only resident who refused to eat dinner that night was not sickened.

State food regulations do not prohibit the use of foraged ingredients in food prepared at care facilities, though they do prevent the use of home-canned foods and unpasteurized milk.