A continued investigation into a listeriosis, or listeria, outbreak that has killed at least one person has expanded to include six states where possibly tainted cantaloupe were consumed, Colorado health officials said Wednesday.

The U.S. Centers of Disease Control and Prevention said this is the first Listeria outbreak in the U.S., which has caused one death in Colorado where the cantaloupes are farmed, and three deaths in New Mexico, linked to cantaloupe produced from the Rocky Ford region of Colorado.

At least 11 cases of listeriosis, a rare and serious illness caused by eating food contaminated with bacteria called Listeria, illness have been reported in Colorado, with 10 in New Mexico, two in Texas, and one each in Indiana, Nebraska, and Oklahoma.

While the investigation into the source of the listeria outbreak is continuing, it is prudent for people who are at high risk for listeria infection to avoid consumption of cantaloupe, Chris Urbina, chief medical officer for the department, said in a written statement.

Because the outbreak has expanded across six states, the U.S. Centers for Disease Control and Prevention (CDC) is coordinating the investigation with the U.S. Food and Drug Administration (FDA) and the U.S. Department of Agriculture (USDA).

On Monday, the Colorado Department of Public Health and Environment said in a release that the state reported 13 listeria cases since the beginning of August.

The fatal cases in New Mexico included a 93-year-old man, a 61-year-old woman, and a 63-year-old man. However, the person who died in Colorado was not identified, CBS News reports.

Symptoms of the infection include fever and muscle aches, diarrhea, headaches, stiff neck and confusion, the Colorado health department said.

Officials said the infection can also cause stillbirths and miscarriages.

Urbina said those mostly likely to be sickened by the bacteria include people over the age of 60, pregnant women and people whose immune systems have been weakened by disease or organ transplants.

Del Monte Fresh Produce is a major seller of cantaloupe in the United States.

Earlier this year the company issued a major recall of cantaloupes harvested from a single farm in Guatemala after federal health officials associated the fruit with an outbreak of Salmonella Panama that sickened 20 people in 10 states, according to a statement from the company.

CDC officials said people in the high-risk groups for contracting the infection should avoid unpasteurized soft cheeses, refrigerated smoked seafood, and deli meats unless they have been reheated to 165 degrees Fahrenheit.