A number of E. coli cases were reported in the Windham/Willimantic area.
The North Central District Health Department said seven cases were confirmed.
All of them required the patients to be hospitalized, according to the department.
Health officials said five of them were mild cases, but two were a severe form of the bacterial infection known as Hemolytic Uremic Syndrome, or HUS.
They said the people with the mild cases have already been released, but one of the two with HUS remains in the hospital.
The Department of Public Health said it is investigating and believes all of the people were infected between mid-December and Christmas time.
However, it said the source of the E. coli has not been found.
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