Salinas, Calif. ? Farmers in the self-proclaimed “Salad Bowl to the World” started plowing their spinach crops under and laying off workers as government inspectors examined fields and packing houses Tuesday for the source of the deadly E. coli outbreak.

After poring over water quality reports, worker hygiene tests and other food safety measures, the inspectors were unable to pinpoint immediately how the bacteria made it into locally grown bagged spinach, causing one death and sickening more than 100 other people across the country.

And it is increasingly unlikely they will ever zero in on the source, said Robert Brackett, director of the Food and Drug Administration’s Center for Food Safety and Applied Nutrition.

FDA investigators visited fields and factories in the Salinas Valley that have been linked to the two companies that recalled spinach products – Natural Selection Foods and River Ranch Fresh Foods.

The teams also inspected other locations, looking for evidence of contaminated runoff; checking for animal droppings in the fields; examining sanitary conditions inside the plants where produce is processed; and taking samples from produce itself. E. coli is commonly spread by human or animal feces.

“They will look for any obvious or even suspected places where this organism could gain access to the produce,” Brackett said.

The absence of any immediate evidence of widespread contamination is good news for the industry, but growers and processors say the scare has already done damage to their products’ reputation, and they are wondering how long it will take for consumers to feel safe eating spinach again.

At least two lawsuits over youngsters who fell ill have already been filed, in New York and Utah.

“If it stays focused on the spinach, it’s still bad,” said Jim Bogart, president of the Grower-Shipper Association of Central California. “Worst-case scenario, where consumers don’t get the message this doesn’t mean all vegetables are tainted, it would be devastating.”