 -- A voluntary recall of beef, veal and bison products has been issued by the Adams Farm Slaughterhouse over concerns the products might contain E. coli bacteria, according to the U.S. Department of Agriculture's food Safety and inspection service.

At least seven people in four states have been identified as infected with a potentially deadly strain of E. coli, O157:H7, that is believed to be linked to the Adams Farm Slaughterhouse, according to the USDA.

Those infected became sick from June 27 to Sept. 4 and were identified in Connecticut, Massachusetts, Pennsylvania and West Virginia, and five patients have reportedly been hospitalized, according to the U.S. Centers for Disease Control and Prevention. Those sickened were 1 to 74 years old, and 57 percent were female, according to the CDC.

Of the five patients interviewed so far, all reported consuming Adams Farms Slaughterhouse products, according to the USDA. In addition to interviews, the CDC utilizes a national database designed to catch emerging outbreaks by looking for DNA matches from bacterial samples of infected people, indicating they were likely infected by the same source.

The products were shipped to various locations, including farmers' markets, retail locations and restaurants in Massachusetts, Connecticut, and eastern New York, according to the USDA. They may have also been shipped to neighboring states, the USDA said.

The products affected by the recall were from animals slaughtered on July 15, 25 and 27 and Aug. 3, 8, 10, 11, 17, 24 and 26 and were packed on various dates from July 21 to Sept 22, according to the CDC.

The products made from animals slaughtered before July 15 were not recalled, in part because any products made earlier than the recall dates would have expired anyway, a federal official told ABC News.

The USDA is still investigating and will expand the recall if needed, a USDA spokesman said.

The products affected have "EST. 5497" inside the USDA mark of inspection. A full list of the recalled products can be found here.

E. coli O157:H7 is a bacterium that can cause potentially life-threatening infections, especially in older adults, young children and people with weakened immune systems. Symptoms can include diarrhea and abdominal cramps. In severe cases, patients can develop a type of kidney failure called hemolytic uremic syndrome.