foodborne illness

Ted S. Warren / Associated Press

Investigators are testing food samples from Chipotle restaurants in the Northwest for E. coli. But so far they haven't found anything. The first batch of food samples tested for E. coli by the Food and Drug Administration came back negative Friday. 

Heath officials in Washington and Oregon are in the midst of an investigation into the source of E. coli linked to Chipotle restaurants.

So far, they don’t know which foods sickened some 40 people, a dozen of whom were hospitalized.

While investigators suspect some kind of uncooked produce, officials don’t know if they’ll ever find the source of the bacteria.

People who say they’ve been sickened by E. coli after eating at Chipotle Mexican Grill restaurants in Oregon and Washington have retained a high-profile, Seattle-based attorney.

So far, the bacteria have sickened 23 people, a number health officials say will grow as the investigation into the outbreak continues. Nine of those people were hospitalized.

The restaurant chain has temporarily closed 43 stores around Washington and the Portland metro area after health officials notified the company about a possible E. coli outbreak linked to the restaurant chain.