Federal investigators have not determined the source of contaminated meat that led Hannaford Supermarkets to issue a recall late Thursday of all ground beef with sell-by dates of Dec. 17 or earlier.

An outbreak of infection from a rare strain of salmonella prompted an investigation by the U.S. Centers for Disease Control and Prevention and the U.S. Department of Agriculture.

The USDA’s Food Safety and Inspection Service said Hannaford’s “limited records” are hindering its ability to determine the supplier that is responsible for the contaminated meat.

Ten of the 14 people who were infected, including four from Maine, said they bought ground beef from Hannaford stores in the period from Oct. 12 to Nov. 20, according to Dr. Stephen Sears, the state epidemiologist. Seven of the 10, including two from Maine, were hospitalized.

Hannaford, which is based in Scarborough and has stores in five states, is the only grocery chain to issue a recall in response to the salmonella outbreak. The USDA would not say whether the contaminated meat could have been supplied to other retailers.

Hannaford has not determined the amount of meat involved in the recall, but it will give refunds for any ground beef within its scope, regardless of whether it’s still in its package, said spokesman Michael Norton. The recall covers the Hannaford, Taste of Inspirations and Nature’s Place labels.

Norton said suppliers deliver boxes of meat to two Hannaford distribution centers, in South Portland and Schodack, N.Y. From there, the meat is delivered to Hannaford’s 179 stores in Maine, New Hampshire, Massachusetts, New York and Vermont. It is ground in the stores, he said.

Norton said Hannaford supplies groceries wholesale to about 30 independent stores, but he did not know how many of those stores buy ground beef from Hannaford.

Norton deferred to the USDA when asked where in the supply chain the contamination occurred. USDA spokesman Neil Gaffney declined to comment on the suspected site of contamination, citing a continuing investigation.

Although the USDA pointed to Hannaford’s record-keeping as an impediment to the investigation, Norton said the grocery chain is “following industry practice and standards in terms of records.”

A lack of record-keeping requirements often makes tracing the source of food-borne illnesses difficult, said Barbara Kowalcyk, founder of the nonprofit Center for Foodborne Illness Research and Prevention. When a source cannot be determined, it’s difficult to know where a contaminated product ends up, she said.

“Sometimes (a recall) starts out small and then two weeks later it gets bigger,” said Kowalcyk. She referred to a widespread recall of ground beef in 2002 as an example of a “rolling recall.”

Kowalcyk’s group advocates for greater record-keeping requirements in the food industry, and for the USDA to have authority to mandate recalls.

Hannaford characterized its ground beef recall as “voluntary” in a news release issued just before midnight Thursday. According to Kowalcyk, all recalls of food products regulated by the USDA are voluntary.

The USDA’s Food Safety and Inspection Service can only recommend a recall, according to the department’s website.

Hannaford “could have done nothing,” said Kowalcyk, although she acknowledged it was “in the company’s best interest” to recall the meat.

Norton said Hannaford has been talking to federal investigators for the past couple of days, but they didn’t determine the connection between the company and the contaminated meat until Thursday. That night, Hannaford removed all ground beef with sell-by dates of Dec. 17 or earlier from its shelves, said Norton.

The scope of the recall, which Norton called “aggressive,” was decided through a collaboration between Hannaford and the USDA, he said.

The Hannaford stores that were linked to illnesses are in Maine, New York, New Hampshire and Vermont, according to the USDA.

Other states that got reports of illness involving the strain of salmonella, which is resistant to common antibiotics, are Ohio, Kentucky and Hawaii, said Sears, the epidemiologist. The cases were reported from Oct. 16 to Nov. 27. The first case in Maine was reported on Oct. 22, he said.

The four Maine residents who were infected are from Cumberland, York, Androscoggin and Waldo counties, said Sears. He said one of them was hospitalized for four days and another was hospitalized for two days.

“They’re all doing fine,” he said.

Sears said the Maine Center for Disease Control and Prevention investigates all cases of salmonella and enters them into a national database, which is how the cases in the various states got connected.

Common symptoms of salmonella infection include diarrhea, abdominal cramps and fever within 12 to 72 hours of eating contaminated food, according to the USDA. Other symptoms are chills, headache, nausea and vomiting. They can last for as long as a week.

Salmonella infection can be life-threatening, especially for people with weakened immune systems, including infants, the elderly and people who have HIV or are undergoing chemotherapy.

The USDA urges people to eat ground beef only if it’s cooked to a temperature of 160 degrees, confirmed with a food thermometer.

Staff Writer Leslie Bridgers can be contacted at 791-6364 or at:

lbridgers@pressherald.com