The root of last summer’s E. coli outbreak linked to California grown celery remains a mystery. After six months of inspections and testing, investigators found no local sources of E. coli contamination – good news for Salinas Valley growers and packers.

Except testing proves not much.

Last July, 57 people were sickened and nine were hospitalized in Minnesota with E. coli O157:H7. All of the victims ate celery or potato salad made with celery at events catered by the same company. Government investigators traced the celery to Martignoni Ranch just north of Gonzales, grown by Costa Farms of Soledad. The celery was cooled and packed by Mann Packing in Salinas.

An attorney representing the victims believes the E. coli contamination started with the caterer, not the growers or packers.

“This report will help get the case resolved,” said William Marler, managing partner of the Marler Clark law firm in Seattle. “We believe the caterer is likely to settle,” he said, since the company won’t be able to point the finger at anyone else.

In late January, the California Department of Public Health completed its initial inquiry into the incident, which state officials conducted in cooperation with the federal Food and Drug Administration. Investigators found no E. coli in seven soil and water samples taken from the ranch. During their inspection, they didn’t see any problems that might have contributed to cross-contamination. And the investigators could not find signs of contamination from a defunct dairy operation next door.