Ontario has been included in a probe into an E.coli outbreak that is being investigated by public health officials.

The Public Health Agency of Canada is investigating six E.coli cases in Ontario.

In all some 30 cases from five provinces are being investigated and the Public Health Agency is linking one death to the outbreak.

Heath officials say most of those who have reported illness said they ate romaine lettuce, but the source of the vegetable hasn't been determined.