Tufts Health Plan warned subscribers Thursday that personal information for about 8,830 seniors enrolled in the insurer 's Medicare plan was stolen . The Watertown - based organization said the theft included the names , birth dates and Social Security numbers of current and former subscribers of the Tufts Medicare Preferred plan . Medical and health information was not included in the theft , Tufts reported . " As soon as we learned of this situation we took immediate action , conducting our own investigations while working very closely and in full cooperation with federal investigators , " Tufts said in a statement . It was not immediately clear how or when the information was stolen . The insurer said in a news release that the theft was brought to Tufts ' attention by federal officials during an investigation that continues . Tufts reported the theft was not caused by an electronic breach , hacking or information technology system vulnerability . A Tufts spokeswoman declined to provide more details on the theft . A spokesman for the Office of the Inspector General for Social Security did not immediately return a phone call late Thursday afternoon . The insurer said it would offer credit monitoring and identity theft protection to people impacted by the theft and to Tufts Medicare Preferred members whose information was not stolen . " We can not convey strongly enough our regret that this incident occurred , " Tufts said in a statement . ;