The Public Health Agency says six people have been hospitalised since the start of the outbreak at Flicks restaurant at Cityside Mall in the city, but most have since been discharged.

The PHA says they are treating the outbreak as a "major public health incident", with eight children under the age of 14 among the suspected cases.

The restaurant, which closed voluntarily on Thursday night, has also been linked to four other cases of E. coli contracted by adults in August.

The cases were investigated at the time and tests carried out on the premises by Environmental Health Officers were returned negative.

Further environmental health inspections were carried out and these were satisfactory, while enhanced surveillance was put in place to monitor cases.

The E. coli outbreak came to light through the enhanced monitoring.

As part of the investigation into the current outbreak, any potential link with the previous cases will be examined, although it is too early to comment further on this at such an early stage.

PHA spokesperson

E. coli is most often found in undercooked meat, especially minced beef, and is also present in the human gut.

The incubation period is up to seven days and Dr Michael Devine from the PHA said he believes more people with food poisoning will come forward.

"We expect therefore to see a further increase in cases as people continue to report symptoms and submit samples for testing. This does not reflect a worsening situation," he explained.

"It's vital that everyone follows some simple rules to prevent the spread of E. coli - not just those with symptoms, but everyone should wash their hands after using the toilet and before eating or preparing food.

"Raw and cooked food should be kept completely separate, raw meat should be cooked through and vegetables and fruit should be washed thoroughly before eating," said Dr Devine.