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PHILADELPHIA (CBS) — Investigators tracking the E. coli outbreak linked to romaine lettuce are now looking at California as the possible source. The outbreak has sickened 32 people in 11 states, including New Jersey — since October.

Nearly a third of the cases are in Los Angeles County.

Experts say the process to identify the source of the outbreak can take time.

Federal health officials say people should throw out all romaine as a precaution.