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, state epidemiologist for communicable diseases for the Washington State Department of Health.

A lawsuit was filed against the company Tuesday by a Washington woman who alleges she contracted an E.coli infection after eating a burrito bowl on Oct. 21 in a Chipotle restaurant in Vancouver.

Minneapolis law firm PritzkerOlsen filed the lawsuit on behalf of Charmaine Mode in U.S. District Court in Western Washington. Documents say she sought treatment Oct. 27 and was diagnosed after falling ill on Oct. 25 with nausea, severe diarrhea and other symptoms.

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