OK, now you really should check your freezer for ground beef you may have stashed away.

The massive ground beef recall initiated in October by the nation's largest beef processor – JBS USA – has gotten even bigger.

The U.S. Department of Agriculture says an additional 5.1 million-plus pounds has been recalled beyond the 6.9 million pounds recalled two months ago for risk of contamination with salmonella newport, a strain of the bacteria that is a common cause of food poisoning.

The 12.1 million pounds of raw beef products including ground beef were produced between July 26 and Sept. 7 by JBS USA at its JBS Tolleson, Inc., processing plant in Tolleson, Arizona.

The USDA's Food Safety and Inspection Service (FSIS) "is concerned that some product may be frozen and in consumers’ freezers," the agency said in an update on its website. "These products should be thrown away or returned to the place of purchase."

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Among the hundreds of products on the list are ground beef sold at Sam's Club stores in more than two dozen states and Walmart stores in Arizona, Colorado, New Mexico, Nevada and Texas. Some products were packaged with the brand names Kroger, Cedar River Farms Natural Beef and Gourmet Burger.

The USDA said the meat was sold at stores nationwide. The packages have an establishment number "EST. 267" inside the USDA mark of inspection. The USDA has found as many as 246 people from 26 states have gotten sick.

Most people infected with salmonella develop diarrhea, fever and stomach cramps within 12 to 72 hours after being exposed to the bacteria, according to the Centers for Disease Control and Prevention. Most people recover from the illness, which usually lasts four to seven days, without treatment.

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But some patients may require hospitalization. The infection can spread from the intestines to other places in the body, the CDC says. Children under the age of 5, adults 65 and older and those with weakened immune systems are more likely to develop a severe illness, the agency says.

The CDC estimates salmonella causes about 1.2 million illnesses, 23,000 hospitalizations and 450 deaths annually in the U.S.

Despite its size, the recall is not the largest ever. The largest nationwide meat recall was 143 million pounds by Westland/Hallmark Meat in 2008 for sale of ground beef, cuts and other meat products potentially infected with mad cow disease.

Prior to that, the largest ground beef recall occurred in 1997 when Hudson Foods recalled 25 million pounds of ground beef with staph bacteria sold to Burger King.

Other major recalls include ConAgra's 2002 recall of about 19 million pounds of ground beef for potential E.coli contamination and the 2007 recall of more than 21.7 million pounds of ground beef for potential E. coli contamination that drove Topps Meat Co. of Elizabeth, New Jersey, out of business.

"This is the biggest recall I can recall in the last several years," said Bill Marler, a Seattle food safety attorney. But in general, "recalls have been down substantially in the last several years," he said.

Still, the broadening case highlights the need for legislation that requires meat producers to refrain from selling products tainted with salmonella as regulations require for other contaminants, including some strains of E. coli, says Viveth Karthikeyan of the nonpartisan U.S. Public Interest Research Group.

"This was already the largest recall of beef in history due to salmonella contamination and proves that we need the USDA to declare for antibiotic-resistant salmonella an adulterant to prevent these hazardous foods from getting onto stores shelves," he said.

The recall's expansion likely came from the USDA's evaluation of the plant's records, "whether it be internal testing at the plant or just cleanliness issues or problems that the plant has been having," Marler said. "That’s what usually prompts the recall to get bigger."

The growing number of illnesses likely led to JBS USA's cooperation in the expanded recall, he says.

Consumers should take the situation seriously and look at the USDA's list showing where products were sold and the labels of the recalled products, Marler says.

"A lot of people put hamburger in the freezer and you have an initial outbreak, and months later I've had clients call and say they got sick because they actually put the hamburger in their freezer and cooked it later," he said.

To handle ground beef safely, "it's not just cooking it to 165 (degrees), it's washing hands, washing cutting boards, all those things that we used to teach people in Home (Economics) but we don't any more," Marler said.

JBS USA has had other recent recalls. Last month, the meat processor recalled nearly 100,000 pounds of ground beef for possible E. coli contamination. The ground beef, produced Oct. 24 at JBS USA-owned Swift Beef Co. in Hyrum, Utah, may have been contaminated with E. coli O157:H7, the USDA says.

In May, JBS USA recalled 35,464 pounds of raw ground beef processed at its Lenoir, North Carolina, facility for possible contamination with hard plastic pieces. No confirmed reports of illnesses were reported in those recalls, the agency says.

Follow USA TODAY reporter Mike Snider on Twitter: @MikeSnider.