A potential outbreak of E. coli O157 is emerging in Wellesley, Massachusetts, outside Boston.

A physician posted on ProMed on June 12, 2013, that “on 20 May 2013, we admitted a 53 year old woman with Escherichia coli O157:H7 who developed classic hemolytic uremic syndrome (HUS) while in hospital. Yesterday [11 Jun 2013], I became aware of 2 more cases. A 44-year-old woman admitted on 6 Jun 2013 with colitis, with the same organism, and who developed HUS by 9 Jun 2013.

“On 11 Jun 2013, a 3rd woman, aged 41 years, entered the emergency department with florid HUS after several days of diarrhea and stool cultures identified with O157:H7.”

Today, boston.com reported that Wellesley public health director Leonard Izzo said officials believe three people have been infected, two seriously. At least one of those infected has been hospitalized, he said.

“We are still trying to identify the source of the infection,” Izzo said.

Izzo said the three people infected are adults and are not believed to be related.

“This is an active investigation and we are working closely with the state Department of Public Health on this,” he said.

State health department spokeswoman Anne Roach said disease trackers are trying to pinpoint the type of infection. She said the department has not heard of any other cases in towns surrounding Wellesley.