The U.S. Centers for Disease Control and Prevention is investigating a listeria outbreak that has killed four people and sickened others across six states, including Texas and New Mexico.

Preliminary investigations by state health officials indicate that the contaminated cantaloupe is the likely source of the listeria outbreak.

Investigators have found that all Rocky Ford cantaloupes have been pulled from Oklahoma's market shelves. Homeland and Wal-Mart removed all their Rocky Ford cantaloupes.

People who think they might still have Rocky Ford cantaloupes should throw them away, said Laurence Burnsed, director of the state Health Department's communicable disease division.

Symptoms of the infection include fever and muscle aches, diarrhea, headaches, stiff neck and confusion, the Colorado Health Department said. The infection can also cause stillbirths and miscarriages.

Listeria outbreaks typically occur in the U.S. two to four times a year. The investigation into the outbreak is still in the early stages and officials who identified the listeria strain in Colorado linked it to other states.

Since the outbreak has gone multi-state, the U.S. Centers for Disease Control and Prevention is coordinating the investigation in conjunction with the U.S. Food and Drug Administration and the U.S. Department of Agriculture.

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.