Two-year-old Olivia Rodriguez got sick, as did 14-year-old Natalie Jones.
"Well for about two days I was just having pain in my stomach, just really bad pain and just constant diarrhea. And it just hurt a lot, " Jones said.
The Centers for Disease Control has now traced the tainted ground beef from a ConAgra processing plant in Greeley, Colorado, reports CBS News Correspondent Bob Orr.
The contamination was first confirmed three weeks ago prompting the company to recall 350-thousand pounds of ground beef distributed in 21 states.
"This action is being taken as a cautionary measure to ensure the protection of public health. Public health is our number one priority," said USDA Secretary Ann Veneman.
The potentially contaminated beef was produced from April 12th to July 11th and was sold under various supermarket names including Safeway and Kroger. All of the recalled ground beef can be identified from a USDA seal on each package bearing the inscription "EST. 969"
"This has just begun," said Elsa Murano, the undersecretary for food safety. She said no E. coli has been found at the plant since July 11.
ConAgra is cooperating with the Agriculture Department, officials said. Veneman, asked if the department will cite the company for violations, said a government investigation at the plant is continuing.
The ConAgra beef scare is the largest since 1997 when Hudson Foods was forced to pull 25 million pounds of ground beef from restaurants and store shelves.
The latest recall comes as congressional investigators are finishing a scathing audit of the USDA which cites poor meat inspections, untrained inspectors, faulty bacteria testing and an overall lack of enforcement."
Food safety expert Caroline Smith DeWaal says that's the government's fault.
"Consumers want meat that is safe and that they can trust to be safe. But under the USDA's program today that's not what they're gonna get," she told CBS News.
E. coli is a bacteria found in the intestinal tracts and feces of livestock.
If it contaminates meat, it can lead to digestive illnesses and potentially death in humans. Health officials have been urging consumers to cook their ground beef to 160 degrees in the center to completely kill the pathogen.
Agriculture officials said no one is currently hospitalized, although some people have been admitted and released, they said.
Testing is under way in other states as public health officials tried to establish the scope of the outbreak.
Americans ate 69.5 pounds of beef per person in 2000, reflecting steady but modest increases since 1993, when consumption fell to 65.1 pounds, officials said.