A huge farm in Salinas, California has decided to voluntarily take back bags of romaine lettuce from its dealer after reports of possible contamination with Listeria.

Listeriosis is a disease caused by a gram-positive bacterium called Listeria that breaks through and reproduce inside human cells. Although, people who are infected show few or no sign of symptoms, these normally consist of fever, muscle aches, diarrhea or nausea.

Some individuals develop more serious indications like meningitis and brain abscesses or even death.

The Tree Leaf Farms revealed the recall of 90 boxes of yield that were transported to an Oregon food service distributor which allegedly sent some of the lettuce to Washington and Idaho, according to a report from Associated Press.

The U.S. Food and Drug Administration (FDA) informed the company that a sample obtained from one of the bags during a routine inspection tested positive for the bacteria.

"We are searching for sources of the contagion but we still have to find out how the lettuce got infected," explained Ken August, spokesman for the California Department of Public Health.

"We are concerned about contamination of food products and we undertake the proper measures so that these are removed from grocery and supermarket shelves as swiftly as possible," he added.

Consumers are informed right away about this occurrence.

In the past, Listeria has hardly ever appeared in produce but an outbreak related to cantaloupe from a farm in Colorado has resulted in 72 infirmities and 16 deaths in at least 18 states.

The state government is working closely with the farm's management to confirm the distribution of the products, most of which were restaurants and canteens in California.

The Salinas Valley has become prominent for its production of lettuce and other crops and is described as the "Salad Bowl of the World."