A linked to shredded iceberg lettuce from central Mexico has expanded to four more states, the U.S. Department of Health and Human Services confirmed to CBS News on Friday. This brings the total number of states affected to nine.

The newly linked states are Illinois, Kansas, Oklahoma and Pennsylvania. The outbreak was previously linked to Indiana, Kentucky, Michigan, Ohio and West Virginia.

The cyclosporiasis outbreak was already the nation's largest. The outbreak expanding to four more states was first reported by the Washington Post.

*This is a developing story and will be updated. *