The same strain of E. coli infected five of the 39 people infected with food poisoning linked to Chipotle restaurants in Oregon and Washington, federal health officials confirmed Wednesday.
DNA fingerprinting links the five cases, the Centers for Disease Control and Prevention said.
"All five people were infected with (shiga toxin-producing E. coli) O26 that has the same DNA fingerprint," the CDC said in a report. Others are still being tested.
The good news is that no one who's reported E. coli in any other states has that same strain, which suggests the outbreak is limited to Washington and Oregon.
"The investigation is ongoing to determine if the ill people ate a common meal item or ingredient that was served at the Chipotle Mexican Grill locations," the CDC said.
"Chipotle Mexican Grill voluntarily closed all of its restaurants in Washington and multiple locations in the Portland, Oregon area until more information is available," the health officials said.
Fourteen of the infected people are sick enough to be in the hospital, but no one has died, the CDC said.
Most E. coli bacteria are harmless, but a few strains produce a toxin, called shiga toxin, which causes stomach upsets, diarrhea, nausea and cramps and that can progress to sometime fatal kidney and organ failure in a few people.