Food delivery service Meals on Wheels has issued an urgent recall of thousands of frozen meals in South Australia after routine testing detected listeria contamination.

The bacteria was found during in a sample of the organisation’s roast lamb and vegetables option prepared at its Kent Town kitchen.

Meals on Wheels on Thursday said it was recalling all frozen meals currently with customers as a precaution, warning they “may pose a risk if not heated correctly after thawing”.

“There are 6000 meals we are looking at recalling,” said Julie Bonichi, the service’s acting chief executive.

There have so far been no reported illnesses connected with the meals, but SA Health said it could take weeks for patients to show symptoms.

“Between eating of food that contains listeria and becoming sick could be between three days and six weeks,” said Dr Fay Jenkins, SA Health’s acting director of public health services.

Ms Bonichi said Meals on Wheels was in the process of alerting customers.

“We still don’t know the exact cause at the moment. We are investigating,” she said.

“We’re working very closely with SA Health and looking at doing further testing to see if we can locate the source.”

Meals on Wheels delivers food to thousands of people, especially elderly residents, across SA on a daily basis.

Elderly people are among the groups at higher risk of listeriosis – the infection caused by the bacteria Listeria monocytogenes.

“Infection is more serious when it occurs in newborn babies, the elderly, immune-suppressed people and pregnant women,” SA Health states on its website.

Symptoms include sudden onset of fever, headache, backache, nausea, vomiting and neck stiffness.

“The symptoms are flu-like – fever and chills, and aches and pains and sometimes some diarrhoea,” Dr Jenkins said.

“If people have been getting frozen meals from Meals on Wheels and you feel you have one of these symptoms, you would go to your doctor, go to your GP if you can, take a poo sample with you.

“They’ll send that sample off for analysis and then assist you as well.”

Ms Bonichi said hot meals, soups and desserts are not affected by the recall.

“We provide meals for people to consume seven days a week, and we have been responding to ensure that [customers] do get their frozen meals delivered over the weekend,” she said.

–ABC