WASHINGTON – More than a half-billion eggs have been recalled in the nationwide investigation of a salmonella outbreak that Friday expanded to include a second Iowa farm. The outbreak has already sickened more than 1,000 people and the toll of illnesses is expected to increase.

Iowa’s Hillandale Farms said Friday it was recalling more than 170 million eggs after laboratory tests confirmed salmonella. The company did not say if its action was connected to the recall by Wright County Egg, another Iowa farm that recalled 380 million eggs earlier this week. The latest recall puts the total number of potentially tainted eggs at about 550 million.

FDA spokeswoman Pat El-Hinnawy said the two recalls are related. The strain of salmonella bacteria causing the poisoning is the same in both cases, salmonella enteritidis.

Federal officials say it’s one of the largest egg recalls in recent history. Americans consume about 220 million eggs a day, based on industry estimates. Iowa is the leading egg-producing state.

The eggs recalled Friday were distributed under the brand names Hillandale Farms, Sunny Farms, Sunny Meadow, Wholesome Farms and West Creek.