The restaurant at the centre of the territory's largest ever salmonella outbreak has remained tight lipped on the progress of an investigation, much to the chagrin of affected patrons.

The restaurant at the centre of the territory's largest ever salmonella outbreak has remained tight lipped on the progress of an investigation, much to the chagrin of affected patrons. Photo: Jeffrey Chan

Diners affected as part of Canberra's largest salmonella outbreak have all been discharged from hospital, more than one week after being exposed to bad mayonnaise.

Some affected diners are considering joining a class action law suit after 140 people fell ill and 15 were hospitalised after eating bad mayonnaise at The Copa restaurant in Dickson.

ACT Health intends to monitor the restaurant for coming months, Chief Health Officer Paul Kelly said, adding that the restaurant had reopened recently after its voluntary closure last week.

“We identified some issues that they needed to address and they addressed them,” he said.

“We’re continuing to monitor the situation over the next few weeks or even months to make sure that’s happening.”

Speaking on ABC Radio, Dr Kelly said there was a possibility that some patients would suffer long term effects from the outbreak.

“The more [people] that you have [affected], the more likely that the relatively rare longer term effects can occur in a small minority of people,” he said.

“As far as I’m aware, the people affected this time didn’t show those signs.”

Dozens of people have responded to statements by The Copa on social media, criticising the response from restaurant owners after Saturday's reopening and demanding a public apology.

The establishment is yet to release a further statement after posting on their Facebook page on Saturday.