The bags had the same "best if used by" date as those identified as the possible source of an E. coli outbreak in the state.
So far, there have been 17 confirmed cases of E. coli and eight hospitalizations.
One victim developed a severe complication that can cause kidney failure, said Doug Schultz, a spokesman for the Minnesota Department of Health.
"As far as we know, this is the first time a laboratory has been able to isolate E. coli from lettuce in an outbreak," said Kevin Elfering, the Department of Agriculture's dairy, food and meat inspection director.
"This is the proverbial 'smoking gun' that we try to identify in every outbreak we investigate," he said in a statement. The department was working with the Food and Drug Administration and the California Department of Food and Agriculture to determine how the bacteria got in the lettuce bags.
Most of the E. coli cases were in the Twin Cities area, but there is one from Martin County in southern Minnesota.
The affected Dole products have a "best-if-used-by (BIUM)" date of Sept. 22, 2005, and Sept. 23, 2005. Stores probably aren't carrying these salads on their shelves any more, but people may still have some at home.
E. coli symptoms include stomach cramps and diarrhea.