An outbreak of E. coli linked to rotisserie chicken salad sold by warehouse club operator Costco Wholesale Corp appears to be over, the U.S. Centers for Disease Control (CDC) said on Tuesday.

The most recent illness in this outbreak reported to CDC started on Nov. 3, the federal agency said.

The U.S. Food and Drug Administration conducted a traceback investigation to determine which ingredient was linked to the illnesses, but the probe could not identify a common source of contamination, the CDC said. 

Five of the 19 sickened people were hospitalized and two developed a type of kidney failure associated with the E. coli strain, STEC O157:H7, the CDC said.

No deaths were reported and the infections occurred in Montana, Utah, Colorado, California, Missouri, Virginia and Washington, the CDC said.

The Costco incident is the latest E. coli outbreak where the source is unknown.

Health officials have still not found the cause of an E. coli outbreak at restaurants owned by Chipotle Mexican Grill Inc.

The Costco outbreak was initially traced to a celery-and-onion mix made by Taylor Farms Pacific Inc used in making the chicken salad.

Taylor Farms, a major producer of fresh-cut vegetables and bagged salads, last month recalled more than 154,000 lots of numerous products from various grocery store chains in 17 states "out of an abundance of caution".

Products were recalled from chains including Costco, Safeway, Starbucks Corp, Wal-Mart Stores Inc, and Target Corp.

Costco's shares were up 0.7 percent at $160.51 in afternoon trading.

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