Shredded lettuce has joined the cantaloupe melon as a recalled food, amid a deadly listeria outbreak that has spread to 25 states in the United States.

A Pittsburgh-based grocery chain, Giant Eagle, has recalled its shredded lettuce after the Food and Drug Administration (FDA) found one package to contain listeria, during a routine test.

The tainted lettuce was produced by River Ranch Fresh Foods LLC and came with a sell by date of Oct.14. In addition the FDA reported that the lettuce was used to make deli ring sandwiches that included:

Giant Eagle Large Italian sandwich Ring (UPC 23755100000)

Giant Eagle Mini Italian sandwich Ring (UPC 24755500000)

Giant Eagle Large New York Sandwich Ring (UPC 22755100000)

 Giant Eagle Mini New York Sandwich Ring (UPC 25755500000)

Giant Eagle Large All America Sandwich Ring (UPC 21755100000)

Giant Eagle Mini All American Sandwich Ring (UPC 26755500000).

There have not been any reports of illnesses caused by the infected lettuce yet, but listeria has an incubation period of a month. Giant Eagle has recalled all the potentially affected products from its store shelves and is using loyalty card purchase history data, trying to contact those who may have purchased any of their products.

A month after infected Cantaloupe melons from Colorado were recalled, the deadly listeria outbreak continues to claim lives, now reaching 23, a record for U.S. food-borne listeriosis outbreaks.

With two more deaths reported in Louisiana on Wednesday, the Centers for Disease Control (CDC) reported a total of 23 deaths caused by the disease:  5 in Colorado, 1 in Indiana, 2 in Kansas, 2 in Louisiana, 1 in Maryland, 1 in Missouri, 1 in Nebraska, 5 in New Mexico, 1 in New York, 1 in Oklahoma, 2 in Texas, and 1 in Wyoming.

In addition, one pregnant woman in Iowa was reported to have suffered a miscarriage after contracting a listeria infection from infected cantaloupe melon, according to state health officials. In general, pregnant women and the elderly are more vulnerable to getting ill from listeria due to their weaker immune systems.

As the death toll now exceeds the number of people who died from a multi-state listeria outbreak linked to hot dogs and deli turkey in 1998, the current outbreak has been classed as the deadliest of its kind. A further 116 people have been reported to have contracted a listeria infection across 25 states, The CDC reported late on Wednesday night.

The outbreak has been traced back to Rocky Ford cantaloupes from Colorado. A total of 300,000 cases of cantaloupes were shipped from the Jensen Farms. Even though the melons were recalled, listeria has an incubation period of a month or more, which means that people who ate contaminated fruit last week may not see illnesses until next month, according to Thomas Frieden, director of the Centers of Disease Control (CDC).