Lea Thompson, chief consumer correspondent for NBC News, had a chance to interview Amber Brister and her mother, Lori Olson.

Amber had contracted E. coli poisoning last September. She had kidney failure and had to have a tube inserted through her abdomen, hooked up to a dialysis machine for 24 hours a day for about 18 days. She couldn’t eat solid foods, had to be fed intravenously, and needed four blood transfusions.

At the same time, 54-yr-old Roi Dahl was also rushed to the emergency room with symptoms similar to Amber’s. Ten similar cases hit Minneapolis hospitals in three days – all from contamination of bagged, pre-washed salad.

Dole Foods issued a voluntary recall for the ‘American Blend’ and ‘Classic Romaine’ bag salads implicated in the outbreak, but not before at least 26 people in three states had gotten very sick.

Olson and others who got sick want some answers, and are suing Dole foods.

To solve the mystery of how bag salad is contaminated, state and federal health officials have launched a wide-ranging investigation. So far, that investigation shows that lettuce implicated in last fall’s outbreak was grown in seven different fields in the Salinas valley of California. It was processed at a Dole packing plant in Soledad. Beyond that, the government has no idea where the E. coli came from.

In California’s Salinas valley, water contaminated with animal feces is the leading suspect in three of the E. coli outbreaks. Investigators found before each one, these low lying fields had been flooded with creek water. A sample of the creek bed tested positive for E. coli.

Scientists believe E. coli bacteria might have been absorbed by the lettuce plant’s root system. If that happens, washing the lettuce won’t do any good – the E. coli is already growing inside.

So what do you do while we wait for the scientists and the experts to figure it all out?

  • Even though bag lettuce is pre-washed, and is labeled ready to eat, experts say it doesn’t hurt to wash it again.
  •  Make sure your hands are clean and you keep the vegetables away from any raw meat.
  • Keep that salad refrigerated.
  • Check the expiration date before you eat it. Even if the lettuce looks good, you should know E. coli can grow quickly in deteriorating greens.