Missouri state health authorities on Thursday confirmed two more cases of listeria illness linked to Colorado-grown cantaloupes and a multistate food-borne outbreak that is already the deadliest in more than a decade.

The Missouri Department of Health and Senior Services said two people were hospitalized after coming down with symptoms of listeriosis, the illness caused by the listeria bacteria. One case was reported in the department’s eastern district, which includes St. Louis and surrounding counties, and another in the northwestern district, which includes Kansas City.

Health authorities had previously confirmed another case — that of a 94-year-old near Springfield, Mo., who died after contracting a listeria infection linked to the outbreak. The primary cause of death, however, was not listed as listeriosis.

Health department authorities did not specify Thursday where the newly confirmed cases were reported, or where the individuals lived. The severity of their illnesses was not clear.

“This is a horrible outbreak. At least 13 deaths thus far, and there are probably closer to 20 already,” said Bill Marler, a Seattle-based lawyer and food safety expert who has filed five lawsuits against the Colorado grower of the melons and retailers who sold them. “I expect that number to go up. This outbreak is not over. The recall is over, but I expect illnesses through the end of October.”