Nineteen people in seven states have been diagnosed with salmonella infections after reportedly eating ground beef from a chain of Maine-based supermarkets, government health officials said.

The illnesses have all been traced to Hannaford, a Scarborough grocery chain that recalled an undetermined amount of ground beef on Dec. 15, according to the United States Department of Agriculture. The beef was marked with a sell-by date of Dec. 17.

The strain of salmonella Typhimurium detected in the outbreak appears to be resistant to common drugs, which can make the foodborne illness more difficult to treat. Of 15 victims who provided information to the Centers for Disease Control and Prevention, seven have been hospitalized. No deaths have been reported.

Illnesses began on or after Oct. 8 and have been reported through mid-December. Illnesses that occurred after that time might not have been reported yet because of the lag between when a person becomes sick and when they reach out to health officials.

Consumers should check their homes for the recalled products, which are listed here.

Salmonella infections can cause diarrhea, fever and abdominal cramps within hours or days. Illness usually lasts four to seven days. 

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