Chipotle Mexican Grill has temporarily closed 43 locations in Oregon and Washington state in response to what health authorities suspect is an E. coli outbreak.

Nearly two-dozen people in the Seattle, WA and Portland, OR areas have tested positive for E. coli in the last two weeks. Four cases were reported in Oregon, and 19 people in Washington have been diagnosed with the food borne illness. Seventeen of them have confirmed visiting a Chipotle restaurant since Oct. 14.

Eight people have been hospitalized so far. No fatalities have been reported. At least one lawsuit has been filed, by a woman who alleges she contracted E. coli after dining at a Vancouver, WA Chipotle on Oct. 21, according to the New York Times.

Chipotle has now voluntarily closed 43 stores in the area, as state and federal officials attempt to determine the outbreak's source.

The Food and Drug Administration and the Centers for Disease Control and Prevention have been called in to aid with the investigation. The FDA is testing food samples from the suspected restaurants, and health officials in both states have begun interviewing those who have tested positive for E. coli. What food items were responsible for the contamination is still unknown.

In a statement, Chipotle confirmed that health department officials “were investigating approximately 20 cases of E. coli, including people who ate at eight of our restaurants in those areas,” and that Chipotle “immediately closed all of our restaurants in the area out of an abundance of caution, even though the vast majority of these restaurants have no reported problems.”

The statement added: “We are working with health department officials to determine the cause of this issue. We offer our deepest sympathies to those who have been affected by this situation."

Chris Arnold, a Chipotle spokesperson, told O'Dwyer's that the company “may be” updating its statement today, “and will continue to update as new information becomes available.”

“Right now, the investigation is ongoing, no cause has been determined, and no connections have been made outside of Oregon and Washington state, so the breadth of the investigation has not expanded,” Arnold said in an email.

As of press time, there is no mention of the outbreak on Chipotle's website, its Facebook page or its Twitter account.

Denver-based Chipotle, which opened its first restaurant in 1993 and now boasts about 1,900 outlets in the United States, Canada, and Europe, has had a rough 2015.

If confirmed, the suspected E. coli outbreak accounts for Chipotle's third food-contamination incident this year.

In August, about 80 customers and 18 employees became sick after eating at a Ventura County, CA Chipotle restaurant. An investigation determined they had contracted gastrointestinal illness Norovirus, which is acquired through contaminated food or water.

A month later, about 60 people were sickened with salmonella after dining at Chipotle locations in Minnesota. The Minnesota Department of Health later determined that outbreak was connected to tomatoes.

Also in September, the company was hit with a class action lawsuit regarding their claims of offering food free of GMOs, a characterization the suit alleges is false and misleading. Recent ad campaigns — along with their “Food with Integrity” mission statement —have highlighted Chipotle’s efforts to offer fresh, local and sustainable ingredients free of GMOs, and have derided the food industry's traditional use of antibiotics and hormones.

Chipotle's stock is down 2.5 percent on news of the possible outbreak. That accounts for a market value loss of about $500 million.

The Wall Street Journal, meanwhile, reported in October that third-quarter Chipotle sales rose 14 percent, to $1.2 billion, lower than analyst expectations. Earnings were up 27 percent, to $140.2 million.