SEATTLE — Chipotle closed 43 of its Pacific Northwest locations after the chain’s third foodborne illness this year sickened about two dozen people – prompting renewed scrutiny of a company that touts its use of fresh ingredients and farm-sourced fare.

Cases of the bacterial illness were traced to six of the casual Mexican food restaurants, but the company voluntarily closed down all of its locations in Washington and the Portland, Oregon, area as a precaution as an investigation continues.

Three people in the Portland area and 19 people in western Washington have gotten sick with E. coli as of Friday. Seventeen of them had eaten at a Chipotle restaurant during the past few weeks. Eight people have been hospitalized but no deaths have been reported.

About a dozen more people were being tested for E. coli on Monday in Washington state and health officials were aggressively searching for more cases, said Dr. Scott Lindquist, epidemiologist for communicable diseases for the Washington State Department of Health.

Lindquist does not expect the number of sick people to increase dramatically, and he said they are not positive yet that the outbreak is limited to people who ate at Chipotle restaurants over the past few weeks.

Chipotle has faced other recent foodborne outbreaks. A salmonella outbreak linked to tomatoes sickened dozens of people in Minnesota according to state health officials. In California, health workers said norovirus sickened nearly 100 customers and employees at a in Simi Valley.

“Having three problems in a couple of months means that Chipotle is not paying attention to food safety like it should,” said Bill Marler, a Seattle food safety lawyer.