Last Updated 7:12 a.m. ET June 5
Health officials in Germany say they are closing in on the origin of the vegetables that are responsible for the deadliest E. coli outbreak in modern times.
Four cases have now been reported in this country as well. In all, more than 2,100 people have been sickened by the bacteria, and at least 20 have died, mostly in Germany.
CBS News correspondent Charlie D'Agata reports that health investigators believe they are close to finding out just which foods caused the outbreak.
Twelve-year-old Johannes Lucka had to fight for his life after falling critically ill with the deadly E. coli bacteria. German doctors put him on a dialysis machine when his kidneys failed. He says he feels better now, but is still dizzy when he sits up.Nearly 200 new cases of E. coli in Germany
4 in U.S. sickened by German E. coli outbreak
Toxic new E. coli strain behind Europe outbreak A representative of the World Health Organization told CBS News that the organization is not certain that contaminated produce - cucumbers, tomatoes and/or lettuce - are to blame for spreading the bacteria, but that, "the evidence is getting stronger."
Studies found 95 percent of those infected ate at least one of those raw vegetables.
But they've yet to pinpoint where they came from. Almost all the sufferers spent time in northern Germany in May, including four Americans who recently returned home.
Suspicions have fallen on a festival in Hamburg. Investigators are also searching for clues at a small restaurant after 17 people fell ill after eating there.
Nearly 200 new cases have been reported in the last two days, and German's health minister warns: the cause of the infection may still be active.
Editor's Note: This story was updated with additional commentary from the World Health Organization.