The cause behind the 2014 listeria outbreak that killed one of the two infected patients has been linked to raw milk, federal health officials said Friday.

The U.S. Centers for Disease Control and Prevention (CDC) was finally able to identify raw milk sourced from Miller's Organic Farm in Bird-in-Hand, Penn., as the most likely cause of the infection in the patients, one from California and the other from Florida.

Agency officials stated that they were notified by the Food and Drug Administration (FDA) about a strain of the bacterium Listeria monocytogenes, which causes listeriosis, found in the farm's raw chocolate milk that closely resembled the strain identified in the two patients. This discovery was made on Jan. 29, 2016.

"Because listeria was recently found in raw milk produced by Miller's Organic Farm, CDC is concerned that conditions may exist at the farm that may cause further contamination of raw milk and raw dairy products distributed by this company and make people sick," the CDC said in a statement. "The investigation is ongoing."

Both patients, who were between the aged of 73 and 81, were hospitalized. The patient from Florida died from the infection.

 Amos Miller, the owner of the farm, said that the company has not been notified of any health problems arising from the raw milk. They are still selling it to their private members.

"I don't know that it was proved it's on the farm here," Miller said. "We hope and pray for the best."

Miller's Organic Farm does not sell its raw milk to retail stores or other locations.

The CDC is recommending that people only drink and eat dairy products that have gone through pasteurization, a process that involves heating milk to a temperature that will kill any dangerous bacteria. The agency added that this advice is particularly important for children under the age of five, pregnant women, older adults and people with compromised immune systems.

Listeriosis is a life-threatening infection with symptoms that include fever, muscle aches and gastrointestinal issues, such as diarrhea. The infection is particularly dangerous because the bacteria can potentially spread from the intestines and into the blood or the central nervous system, causing either a bloodstream infection or meningitis.