Food safety experts are suggesting that contaminated tomatoes and infected food service workers might have played a role in a Salmonella outbreak that has sickened 171 people in 19 states. Most of the states affected are in the eastern half of the nation.

The CDC said the outbreak appears to be over. The agency said the hunt for the source of the outbreak may take days to weeks, according to CIDRAP News.

David Acheson, MD, chief medical officer for the FDA’s CFSAN, told the Associated Press yesterday that if fresh tomatoes are to blame in the outbreak, it will be more difficult to trace the original source of the contamination than it was in the recent E. coli O157:H7 outbreak linked to fresh spinach.

FDA is depending on the CDC and state and local health investigators to consider food workers as the possible source of contamination.