A recent listeria outbreak traced to a kitchen at Los Angeles International Airport (LAX) has led a handful of airlines to suspend using an on-site catering company for flight meals. American Airlines, Virgin Australia and Delta Air Lines all reported they have temporarily stopped using Gate Gourmet after a recent inspection found traces of listeria at its facilities.

Listeriosis is typically caused by ingesting contaminated food, according to the CDC. An estimated 1,600 cases of listeriosis in the U.S. are reported annually, and pregnant women, newborns, older adults and people with weakened immune systems are most susceptible. Symptoms include muscle aches, stiff neck, fever and confusion. They can appear similar to those of the flu in women who are pregnant.

American Airlines told International Business Times in a statement that it “ceased using” Gate Gourmet for its onboard catering on Nov. 1. However, the airline clarified that signs of listeria were found neither on food nor in food preparation surfaces during the inspection.

“Based on our concerns over the progress of the action plan, we made the decision to suspend the use of catering from this location,” American Airlines said. “While no reports of illness related to the LAX Gate Gourmet catering operation have been reported to American, out of an abundance of caution, we made this decision because we felt it was the right thing to do for our customers and team members. Although we use Gate Gourmet as a caterer in other locations, we currently do not have any information that suggests that Listeria has been detected at any other facility.”

The carrier added that those who do not “receive their standard catering service will receive an electronic travel voucher for use on a future flight.”

Los Angeles International Airport A passengers waits for a Delta Airlines flight in Terminal 5 at Los Angeles International Airport, May 4, 2017 in Los Angeles, California. Photo: ROBYN BECK/AFP/Getty Images

Delta Air Lines announced last week that it “has temporarily adjusted catering operations so Gate Gourmet can take more aggressive actions to further improve food safety,” according to Forbes.

“This move is out of an abundance of caution for the health and safety of our customers,” Delta Air Lines said in a statement. “Delta has made alternate catering arrangements so there is no interruption to its on-board food offerings.”

Virgin Australia alerted its passengers to the incident last week, Forbes reported. The airline — which runs between Sydney and LAX — said in a statement that “there will be limited catering available on flights from Los Angeles.” As the result, the carrier is reportedly providing customers with food vouchers.

American Airlines said in its statement that Gate Gourmet was cooperating with state and federal officials and “immediately implemented a comprehensive corrective action plan to address this issue.” The airline added that it brought in its own outside experts to review and monitor the incident.

“While no reports of illness related to the LAX Gate Gourmet catering operation have been reported to American, out of an abundance of caution, we made this decision because we felt it was the right thing to do for our customers and team members,” the airline told IBT. “Although we use Gate Gourmet as a caterer in other locations, we currently do not have any information that suggests that Listeria has been detected at any other facility.”

Gate Gourmet spokeswoman Catherine Nugent told Forbes that Gate Gourmet remains “committed to delivering a safe and efficient service.”

“We reaffirm that our LAX facility is operating without restriction and continues to comply with all local and federal regulations,” Nugent said. “When we identified the issue on non-food contact areas at our LAX catering kitchen, we immediately enacted our remediation cleaning protocols with an aggressive treatment and comprehensive testing plan.”