Both farms are linked to businessman Austin "Jack" DeCoster, who has been cited for numerous health, safety and employment violations over the years. DeCoster owns Wright County Egg, the original farm that recalled 380 million eggs Aug. 13 after they were linked to more than 1,000 reported cases of salmonella poisoning.
Another of his companies, Quality Egg, supplies young chickens and feed to both Wright County Egg and Hillandale Farms, the second farm that recalled another 170 million eggs a week later.
Jewanna Porter, a spokeswoman for the egg industry, said the two companies share other suppliers as well, but she did not name them.
The cause of the outbreaks is so far unknown, as Food and Drug Administration investigators are still on the ground at the farms trying to figure it out. The federal Centers for Disease Control has said the number of illnesses, estimated as high as 1,300, would likely grow.
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DeCoster is no stranger to controversy in his food and farm operations:
In 1997, DeCoster Egg Farms agreed to pay $2 million in fines to settle citations brought in 1996 for health and safety violations at DeCoster's farm in Turner, Maine. Then-Labor Secretary Robert Reich said conditions were "as dangerous and oppressive as any sweatshop." He cited unguarded machinery, electrical hazards, exposure to harmful bacteria and other unsanitary conditions.
In 2000, Iowa designated DeCoster a "habitual violator" of environmental regulations for problems that included hog manure runoff into waterways. The label made him subject to increased penalties and prohibited him from building new farms.
In 2002, the federal Equal Employment Opportunity Commission announced a more than $1.5 million settlement of an employment discrimination lawsuit against DeCoster Farms on behalf of Mexican women who reported they were subjected to sexual harassment, including rape, abuse and retaliation by some supervisory workers at DeCoster's Wright County plants.
In 2007, 51 workers were arrested during an immigration raid at six DeCoster egg farms. The farm had been the subject of at least three previous raids.
In June 2010, Maine Contract Farming - the successor company to DeCoster Egg Farms - agreed in state court to pay $25,000 in penalties and to make a one-time payment of $100,000 to the Maine Department of Agriculture over animal cruelty allegations that were spurred by a hidden-camera investigation by an animal welfare organization.
It is unclear what role DeCoster's company played in the current salmonella outbreak. The FDA investigation could take months, and sources of contamination are often difficult to find. The current recall goes back to April, and many of the eggs have already been consumed.
Michael Taylor, the FDA deputy commissioner in charge of the agency's food safety strategy, said the government would continue to investigate the outbreak and touted new safety regulations that went into effect in July.
"Well, we have to systematically work to prevent these problems and looking into this case in particular to see what went wrong in these facilities. But we know if we put in place the right preventive measures we can reduce the risk of these problems. We have new rules coming into effect just this summer, actually [that] we think will help in the future," he told CBS' "The Early Show" Saturday.
Still, DeCoster's Wright County Egg is already facing at least two lawsuits related to the egg recall. One is from food distributor Dutch Farms, which says the company used unauthorized cartons to package and sell eggs under its brand without its knowledge.
The other is from a person who said they became ill after eating tainted eggs in a salad at a restaurant in Kenosha, Wis.
The CDC said investigations by 10 states since April have identified 26 cases where more than one person became ill. Preliminary information showed that Wright was the supplier in at least 15 of those.
Almost 2,000 illnesses from the strain of salmonella linked to both recalls were reported between May and July, nearly 1,300 more than usual, the CDC said. No deaths have been reported.
The most common symptoms of salmonella are diarrhea, abdominal cramps and fever within eight hours to 72 hours of eating a contaminated product. The disease can be life-threatening, especially to those with weakened immune systems.
CBS News medical correspondent Dr. Jennifer Ashton gave some basic tips to minimize risk of salmonella from eggs:
Avoid consuming raw or undercooked eggs.
Don't cook with eggs sitting out for more than two hours.
Always wash your hands after handling egg products.
If in doubt, throw it out. If you don't know where your carton came from, get rid of it.