LOS ANGELES — California’s Salinas Valley is grappling with a new outbreak of E. coli contamination linked to packaged salads.

The U.S. Centers for Disease Control and Prevention said Monday that the latest multistate outbreak, which sickened eight people in upper-Midwest states and 16 in Canada, involves a different E. coli strain than the one involved in a previous set of illnesses announced before Thanksgiving.

The outbreaks, however, share a common geographical origin: lettuce harvested in California’s Salinas Valley, according to the CDC.

This time, Fresh Express Sunflower Crisp salads were the “likely source” of contamination, the agency said. Although those packaged salads include romaine lettuce, the agency said it has not narrowed the outbreak to a specific ingredient. Consumers are advised to throw away salad mixes with a “best-before” date of Dec. 7 and a UPC number “0 71279 30906 4” and Lot Code “Z” in the top right corner, the agency said. No recall has been issued.

In a recorded consumer hotline message, Fresh Express said the company halted its Salinas Valley romaine harvesting after a November outbreak that has sickened more than 100 people. A separate romaine outbreak over the summer sickened 23 people in 12 states.

Last year, a series of outbreaks linked to California romaine lettuce sickened more than 250 people.

The culprit in each of those previous outbreaks was identified as a strain of E. coli known as 0157:H7 that produces a potent toxin that causes symptoms including diarrhea, vomiting and kidney failure. The bacteria are commonly found among stockyard animals such as cows.