The Salinas Californian’s story Local produce linked to E. coli outbreaks reports that contamination of lettuce and spinach grown in the Salinas area is blamed in three major food-illness outbreaks since 2002, although state investigators have been unable to pinpoint the sources of bacteria that killed one elderly woman and sickened at least 114 other people.
From the article:

All three incidents, two in California and one in Washington state, involved the most dangerous form of the bacteria E. coli — type O157:H7.
This form, which can lead to kidney failure in the worst cases, is more often transmitted in food handling than during cultivation or processing. But in two of the outbreaks, multiple contaminations of lettuce from the same shipments in different places suggest that trouble occurred before the produce reached food preparers.
“The multiple sources of romaine involving two distant states suggest that contamination was not caused by consumers or a food handler,” said a Washington State Department of Health report released in March 2003. “It is likely contamination occurred prior to lettuce distribution.”
At least 16 victims were hospitalized with symptoms that included severe cramping, vomiting and bloody diarrhea, according to official reports. All survived except for a resident of a Bay Area retirement community, who ate contaminated spinach in October 2003, and a fellow resident, who was hospitalized for bacterial infection and died days later of an unrelated cause, the San Mateo County Health Services Agency said.
Following each of the outbreaks reported between July 2002 and October 2003 — at a drill-dance camp in Washington state, a restaurant chain in San Diego County and the retirement community in Portola Valley — California health officials completed extensive investigations around Salinas.
All three outbreaks involved produce that had been cut in advance for convenient use, as opposed to heads or bunches.