Dallas ? A foodborne illness that contributed to the deaths of three people has been traced to a second production facility operated by Blue Bell Ice Cream, a company spokesman and health officials said Tuesday.

A 3-ounce cup of ice cream contaminated with listeriosis was traced to a plant in Broken Arrow, Oklahoma, Blue Bell spokesman Gene Grabowski said. He said the cups with pull tab lids are not sold in retail locations and instead are shipped in bulk to “institutional accounts” in 23 states that comprise less than 5 percent of the company’s sales.

Blue Bell expanded a recall that was announced earlier this month to include three flavors that come in the cups: chocolate, strawberry and vanilla. The production line in Broken Arrow that makes the flavors has been stopped, but work continues in other parts of that plant.

Ten products recalled earlier this month by the company were from a production line at a plant in Brenham, Texas, where the company is based.

The recall began when five patients at Via Christi St. Francis hospital in Wichita, Kansas, became ill with listeriosis while hospitalized at some point from December 2013 to January 2015. Officials determined at least four drank milkshakes that contained Blue Bell ice cream. Three of the patients later died.

Sara Belfry, spokeswoman for the Kansas Department of Health and Environment, said inspectors discovered the contaminated 3-ounce cups after testing other Blue Bell products at the hospital. Kansas health officials are continuing with testing to determine whether any other cases of infection are associated with the strand of bacteria detected in the Blue Bell products, she said.

Via Christi Health said in an online statement that upon learning of the contamination, the hospital removed Blue Bell ice cream from all of its care locations.

Listeriosis, also known as listeria, is a life-threatening infection caused by eating food contaminated with bacteria called Listeria monocytogenes, according to the U.S. Centers for Disease Control and Prevention. The disease primarily affects pregnant women, newborns, older adults and people with weakened immune systems.

Stan Stromberg, director of food safety for the Oklahoma Department of Agriculture, Food and Forestry, said the freezing temperatures used by Blue Bell to manufacture its products will not kill listeriosis but prevent bacteria from growing and spreading.

“It’s unusual to find listeria in ice cream because it’s pasteurized and immediately packaged and frozen,” Stromberg said. “The pasteurization would have killed the bacteria. It could have been introduced between pasteurization and packaging.”

Grabowski said the recall is the first in the company’s 108-year history and that it’s working to determine how the bacteria were introduced. One theory to consider is whether the bacteria accompanied an ingredient, he said.

“It’s unlikely that the problem lies with any sort of process that’s been ongoing with the plant,” Grabowski said.

In addition to the Broken Arrow plant, the company has two plants in Brenham and one in Sylacauga, Alabama.