Two Iowa farms that together recalled more than half a billion potentially tainted eggs this month share close ties, including suppliers of chickens and feed.

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.