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Mr. Dalli told the EU Parliament in Strasbourg, France, that information must be scientifically sound and foolproof before it becomes public.

In outbreaks, it is not unusual for certain foods to be suspected at first, then ruled out. In 2008 in the United States, raw tomatoes initially were implicated in a nationwide salmonella outbreak. Consumers shunned tomatoes, costing the tomato industry millions. Weeks later, jalapeno peppers grown in Mexico were determined to be the cause.

In the current E. coli outbreak, tests are continuing on sprouts from an organic farm in northern Germany but have come back negative so far.

But Dr. Rodier said those results don’t necessarily exonerate the vegetables.

“Just because tests are negative doesn’t mean you can rule them out,” he said. “The bacteria could have been in just one batch of contaminated food, and by the time you collect specimens from the samples that are left, it could be gone.”

He said food-borne outbreaks are difficult to contain because they involve multiple industries, government departments and, in Germany’s case, several layers of bureaucracy to report numbers. That results in a slight reporting delay, which makes it harder for experts to know whether an outbreak is peaking or not.

The outbreak has killed 22 people — 21 in Germany and one in Sweden.

Germany’s national disease control center, the Robert Koch Institute, on Tuesday raised the number of infections in Germany to 2,325, with another 100 cases in 10 other European countries and the United States. The number of victims hospitalized in intensive care with a rare, serious complication that may lead to kidney failure rose by 12 to 642.

The institute said the number of new cases is declining — a sign the epidemic might have reached its peak — but added it was not certain whether that decrease will continue.

In a major difference from other E. coli outbreaks, women — who tend to eat more fresh produce — are by far the most affected this time. The majority of the victims in Germany are between 20 and 50 years old and tend to be highly educated and very fit and lead healthy lifestyles, investigators said.

“What do they have in common? They are thin, clean pictures of health,” said Friedrich Hagenmueller of the Asklepios Hospital in Hamburg, Germany.

David Rising in Hamburg, Raf Casert in Brussels and Juergen Baetz in Berlin contributed to this report.