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A U.S. investigation that initially focused on raw tomatoes is now examining jalapeno and serrano peppers. ((Shari Vialpando/Associated Press))

The U.S. Food and Drug Administration on Thursday eased its warning on tomatoes, saying it's safe to eat tomatoes again as the salmonella outbreak slows.

The number of cases of salmonella as of Wednesday totalled 1,196, including four cases in Canada. David Acheson, assistant commissioner for food protection, said investigators were continuing to search for the original point of contamination.

Investigators initially focused on raw red tomatoes as the possible source but later widened the probe to include fresh serrano peppers, fresh cilantro and fresh jalapeno peppers.

The FDA is continuing to caution elderly people, infants and those with compromised immune systems against eating raw jalapenos and serrano peppers.

The FDA said early in the investigation that officials found a possible link between the salmonella strain and tomatoes. But they noted that tomatoes harvested in April and May are not likely still in production and destined for the marketplace.

The investigation is now turning to a Mexican supplier that packages peppers from different farms, the FDA said.

Four Canadians have been infected with the same strain of salmonella, according to the Canadian Food Inspection Agency and the Public Health Agency of Canada. Three of the people became ill after returning home from a trip to the U.S.

Salmonella bacteria normally live in the intestinal tracts of animals and birds, but can be transmitted to humans who eat food contaminated with animal feces. Salmonella causes intestinal problems in humans, resulting in diarrhea, fever and cramps.

With files from the Associated Press