Four people in the U.S. were apparently sickened by the food poisoning outbreak in Europe.

Health officials say three -- two women and a man -- are hospitalized with kidney failure.

It's a complication of E. coli that has become a hallmark of the outbreak. One of the four fell ill while on a plane to the U.S.

All four were in northern Germany in May. Though they didn't stay at the same hotel or eat at the same restaurants, officials are confident that they were infected with E. coli in that country.

Two other cases are being investigated in U.S. service members in Germany.

More than 1,800 people have fallen ill, nearly all in Germany.

The US Food and Drug Administration said Friday it believes US foods remain unaffected by a deadly European outbreak of Escherichia coli (E. coli) bacteria, which so far has been linked to more than 2,000 infections in Germany alone.

The FDA said the US receives very little fresh produce from the European Union, but as a safety precaution the administration has increased surveillance of fresh tomatoes, cucumbers, lettuce and raw salads from the affected areas.

"There is no reason for Americans to alter where they shop, what they buy or what they eat," the administration said.

The outbreak was centered in Germany, but after spreading to 12 countries appeared to be stabilizing, a senior German doctor said Friday, as the death toll rose to 19.

Regional German health authorities have reported more than 2,000 cases of people falling ill with EHEC poisoning, with symptoms including stomach cramps, diarrhea, fever and vomiting, AFP reported.

The Associated Press contributed to this report