Chief Health Officer Paul Kelly said on Wednesday morning that he expected the official numbers to keep rising, as he knew of even more people admitted to hospital on Tuesday night.

"By Tuesday afternoon it became clear we had to ramp up our response, the official figures are still being worked out and we will report on those later in the day," he said.

"By Tuesday afternoon it was clear we had over 50 cases, and most of those had been treated at either Calvary or Canberra Hospital emergency departments. There were nine admissions, I know that there were more overnight, and that will rise, we will have that update later today [Wednesday]."

The Canberra Times received reports from numerous readers who have fallen ill as part of a salmonella outbreak in recent days, after eating at The Copa Brazilian Churrasco in Dickson in its opening weekend.

Dr Kelly told ABC radio on Wednesday morning that the investigation was continuing, and it had been hard to pin down what caused the outbreak because of the restaurant's buffet style. This meant "pretty much everyone eats everything".

A spokesman from The Copa - open for less than a week - confirmed on Tuesday that it was working with a team from ACT Health, having voluntarily closed its doors this week citing ventilation exhaust issues.

An ACT Health spokeswoman said she could not name the establishment involved in investigations, but The Canberra Times has been contacted independently by several people who have fallen ill after eating at The Copa.

Dr Kelly said he was first notified by Calvary Hospital staff about 10am on Monday regarding the influx of patients, who have now been confirmed as having contracted salmonella.

Canberra and Calvary hospitals have enacted their emergency response plan with more sick patients presenting in emergency departments on Tuesday.

''It's usually from food and the most likely thing is it's probably egg-based,'' he said. ''But it can be chicken, it can be salads.''

On Tuesday, Dr Kelly said five people were in hospital and 22 other cases had been reported, but that number has now risen significantly.

He said it appeared those affected by food poisoning symptoms had eaten at the same restaurant, where a buffet-style meal had been served.

He confirmed inspections were being carried out on site and investigators had taken swabs of surfaces and samples of available food from the weekend.

''Everyone we know of so far ate at this particular place on either Saturday or Sunday,'' he said.

''The restaurant is voluntarily closed. They'll remain closed until we're satisfied that it's safe.''

Dr Kelly said investigators should have more conclusive results by Wednesday afternoon and urged people to contact ACT Health's health protection service on 6205 1700 if they were showing similar symptoms.

Dr Kelly said it was ''one of the biggest'' cases in recent years in Canberra, which has now recorded five widespread cases of food poisoning since late 2010. ''We've seen four of a similar size,'' he said. ''Each of them have been associated with egg.''

Numerous people have contacted The Canberra Times, reporting that they and fellow diners at The Copa had been forced to seek medical treatment after eating at the restaurant on the weekend.

Marcela Valenzuela said her mother Zunilda Leon got food poisoning after eating at the restaurant.

Farrer woman Tijana Ruzic spent Tuesday looking after her husband when he fell violently ill on Monday night, one day after eating at the establishment. ''My husband and his whole family attended for a Mother's Day dinner,'' she said.

Ms Ruzic said of the table of eight or nine, seven fell ill. None of the group have been hospitalised. ''However we need to provide samples to the doctor … It's horrible. He can hardly move. He was up with a fever all night.''

Another woman who contacted The Canberra Times said her friend was sent home from hospital because there wasn't enough space to accommodate the number of people presenting with food poisoning symptoms.

''When arriving at the Canberra Hospital my friends were quickly asked if they ate at The Copa Brazilian Churrasco,'' she said.

''Around 20 people were at the emergency room and waiting room with the same symptoms. Today I received an SMS of another group of friends who were heading to the hospital because overnight they developed the symptoms.''

She said her friends, who had been performing at the restaurant reported vomiting and stomach pains. Another person who contacted The Canberra Times said eight people from their table of 10 fell ill after dining at the establishment on Sunday.

Marcela Valenzuela described the emergency department of Calvary Hospital as ''like a war zone'' with around 20 people separated from the other emergency patients in a makeshift ward on drips, antibiotics and some even morphine.

Her mother was first admitted with food poisoning on Monday morning, but like many others was treated, sent home, then admitted again.

Ms Valenzuela and her mother were part of a group of 10 dining at the Copa Brazilian Churrasco on Saturday night, with only Ms Valenzuela and friend Carlos Obando escaping illness - as both happened to be on antibiotics. The first Ms Valenzuela knew something was wrong was when a friend messaged her on Monday to ask if she was feeling OK.

''She said, 'they're falling like flies, there are a few people already in hospital' … I rang my mum and she goes, 'I've been up all night with diarrhoea and vomiting', so we brought her in [to hospital],'' she said. ''I can't blame [the restaurant] because we don't know yet where it comes from - maybe it was something that they bought that was already contaminated.''

She said the scenario could have been worse had the fully booked restaurant not been forced to close around 7pm on Saturday due to faulty exhaust fans, with patrons not charged for their meals.

But the free dinner was not enough to make up for the immediate medical costs. ''Who's going to pay the bill here?'' Mr Obando asked.

- with Fleta Page and Lucy Rickard

Do you know more? Let us know via email: online@canberratimes.com.au.