Holiday makers struck down with vomiting and diarrhoea after visiting Tangalooma off the coast of Brisbane are angry with how the popular island resort handled the drinking water contamination.

Key points: Initial tests of the drinking water at the site returned positive samples of E.coli

Initial tests of the drinking water at the site returned positive samples of E.coli All guests have been advised to boil their drinking water or use commercially supplied bottle water

All guests have been advised to boil their drinking water or use commercially supplied bottle water Queensland Health is preparing to send more investigators to the resort to continue testing

Health authorities are investigating the source of the contamination after more than 50 people fell ill with gastroenteritis on Moreton Island in a matter of days.

A spokeswoman for Tangalooma Island Resort said initial tests on the water by authorities returned positive samples of E.coli (Escherichia) bacteria.

"Some of our guests and staff have reported illness consistent with nausea, vomiting, diarrhoea, stomach cramps and a general feeling of being unwell," she said.

Dr Kari Jarvinen from the Metro South Public Health Unit said further testing was being undertaken.

"All guests and staff have been advised to boil their drinking water or use commercially supplied bottled water until the issue is resolved," Dr Jarvinen said.

"Anyone on the resort or anyone who has recently visited the resort should be alert for symptoms of gastroenteritis and seek medical advice if they have concerns."

'Don't drink the water'

Peter Morris and his partner Samantha had vomiting and diarrhoea after spending a week at the resort.

He said she became quite ill on Saturday night after they had checked out and returned to the Gold Coast.

"I tried very hard to get an after-hours doctor here at Broadbeach and ended up getting an ambulance and she was taken to Robina Hospital," Mr Morris said.

Peter Morris and Samantha Todd became sick after a week-long holiday at Tangalooma Island Resort. ( ABC News: Tom Forbes )

"She was definitely worse than me and she's got a medical condition that means that if she can't take her medicine orally it becomes life-threatening. So she had to have injections."

Mr Morris said he had heard nothing from the resort despite management saying it had contacted 3,000 guests following the outbreak.

"They have made no attempt to contact me or my friends and they have our email and mobile details," he said.

"They're very bad at communication."

David James, the director of the resort, said staff were contacting 3,000 people who had visited or stayed at the resort over the past few weeks.

"We're still in that process but [we've been] doing that for the last day or so," he said.

Kate McCorkindale was staying at accommodation near, but not owned, by the resort on the weekend for a friend's 30th birthday.

She said her group did not find out about the contamination until 24 hours after resort guests were told.

"We found out from other resort guests who came to visit us in our house. We were drinking the water and they said, 'Oh stop, don't drink the water'," she said.

"We were really disappointed with the response."

The resort said when people first started getting sick mid-last week it appeared to be a norovirus outbreak. ( ABC News: George Roberts )

Ms McCorkindale said the owner of the house where she was staying was also in the dark.

"Perhaps it wasn't the resort's responsibility, but no-one let us know," she said.

The water supply for the resort and properties surrounding it is run by the resort.

Seven people in her group of 16 had mild cramping and diarrhoea.

A one-year-old was among those who got sick.

Resort guests have been advised to boil their drinking water or use commercially supplied bottled water. ( ABC News: Gregor Salmon )

It was Courtney Jefferies's birthday that brought the group to the island.

She said she would write a formal complaint to the resort over the handling of the incident.

"Whilst we were staying in private accommodation we were still staying at their resort, utilising their facilities and drinking their water, and in my view they have a duty of care to all persons," she said.

"It's really quite disgusting, the lack of communication."

Kristy Lambert, who is pregnant, says she hasn't experienced any symptoms of the contamination unlike her husband. ( ABC News: Scott Kyle )

Kristy Lambert, who is 15 weeks' pregnant, was also among the group of 16.

"We had babies staying with us that obviously had formula bottles being made up and being pregnant, water was the only thing I could drink," she said.

"So I was going to town on the water all day Friday, all day Saturday and it was Saturday afternoon that we then got told from another guest that was staying at the resort, 'hey, don't drink the water'.

"It's a bit daunting to think that something as simple as water could have passed on those germs."

E.coli bacteria found

Resort director Mr James said when people first started getting sick mid-last week it appeared to be a norovirus outbreak, but on Saturday testing confirmed an E.coli contamination.

"As soon as we found that out we obviously stopped all water supply into the resort itself and we're supplying all of our guests with water … whilst we work through this issue," he said.

Mr James said that meant "testing, testing, and more testing" to determine how the contamination happened.

"It's never happened before and that's what's got us a bit stumped here," he said.

He said the main water reservoir was treated on Saturday and the resort was waiting to see if it would be given the all clear.

"All we're worried about is making sure everyone has a great holiday," he said.

About 15 to 20 resort staff were among those to be affected.

The resort said it had carried out a chlorination treatment to improve the water quality. ( YouTube: Tangalooma Island Resort )

A spokeswoman said all the water is sourced from the underground water table and filtered through the resort's water-treatment plant.

"The quality and safety of our water-treatment facility and water supply is regularly audited by independent experts to meet all regulatory and safety requirements," she said.

"To date there have been no previous issues of such a contamination in the resort's long history."

Premier Annastacia Palaszczuk said the resort has a duty of care to its guests.

"I've asked my director-general to immediately send a public health expert over to the island to conduct an examination of that," she said.