More than 50 people have been sickened with gastroenteritis at Tangalooma Resort on Moreton Island and government health investigators say E coli bacteria was found in the drinking water.

Investigators zeroed in on an underground aquifer on the island as the source of the contamination after people started coming down with awful vomiting and diarrhea last week. 

"It is a private water supply that is maintained and looked after by the facility managers," said Dr. Kari Jarvinen from the Metro South Public Health Unit.  "Bacteria must have entered into the water supply, whether through the storage tanks or a breakage."

Officials with the resort are contacting 3,000 people who have visited or stayed there over the last few weeks.  

"Anyone on the resort or anyone who has recently visited the resort should be alert for symptoms of gastro-enteritis and seek medical advice if they have concerns," said Dr. Jarvinen.  "Initial reports to Queensland Health involved 50 cases, however the exact number of people potentially affected is unknown."