Officials in Washington and Oregon confirmed Tuesday that 37 people have taken ill with the E. Coli bacteria, up from 22 confirmed illnesses on Monday.

Chipotle restaurants are a suspected source of the bacteria, and the Centers for Disease Control and Prevention praised the restaurant chain for closing 43 of its restaurants in the I-5 region between Portland, Ore. and Seattle, Wash. But the CDC had little additional information to share about the exact cause on Tuesday.

"We don't yet know of a vehicle, which food caused it, or even with certainty that all of the cases that are identified there are related to each other," Dr. Tom Frieden, director of the CDC, said Tuesday.

If Chipotle is discovered to be a source of the outbreak, it would be the chain's third foodborne illness in the Pacific Northwest this year.

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