Reversing course, German officials said initial tests published June 6 provided no evidence sprouts from an organic farm in northern Germany were the cause of a deadly E. coli outbreak.

According to Associated Press reports, health officials had identified German bean sprouts as the likely source of the E. coli outbreak that has killed 21 people and infected thousands, including four cases in the U.S.

According to The Guardian, the state of Lower Saxony in Germany issued a warning to consumers to stop eating bean sprouts on June 3, but also continued a warning against eating raw cucumbers, leafy greens and tomatoes.

Restaurants involved in the outbreak received sprouts from Uelzen, where a factory produces 18 types of sprouts, according to the Guardian.

The Wall Street Journal reported one of the sprout grower's employees was ill with an E. coli infection, although the paper didn't say if it was the rare strain linked to the outbreak.

"This all, in combination with the different clues, makes the chances of this (company) being the source pretty high," said Gert Hahne, spokesman for the German agriculture ministry, according to the Journal.

The German government originally blamed Spanish cucumbers as the source of the outbreak.

The E. coli strain, known as STEC O104:H4, has never been reported in the U.S., according to federal food safety regulators. The four patients in the U.S. recently visited Hamburg, Germany.

According to Reuters, the Food and Drug Administration has increased surveillance of imported fresh tomatoes, cucumbers, lettuce and raw salads "from areas of concern," but there's no indication any food in the U.S. has been tainted by STEC O104:H4.

According to FoodSafety.gov, sprouts have been linked to at least 30 foodborne illness outbreaks, mostly of salmonella and E. coli.

This spring, at least 22 cases of Salmonella Newport were linked to alfalfa sprouts from Caldwell Fresh Foods, Maywood, Calif.

In January, Jimmy John's Gourmet Sandwiches switched from alfalfa to clover sprouts after at least 94 people became sick in an outbreak linked to sprouts supplied to the restaurant chain by Tiny Greens Organic Farms.

Another recall this year came from Jonathans Sprouts of Rochester, Mass., after samples tested positive for salmonella. No illnesses were linked to that recall.