A Brisbane COVID-19 quarantine hotel is in lockdown as health authorities investigate how an infected traveller contracted the virus.
The infected person was staying on the same floor as at the Hotel Grand Chancellor as another infected traveller now at the Princess Alexandra Hospital.
That patient had contact with a doctor who later became infected with coronavirus, forcing the hospital into lock down.
"Case one is the person brought into the hospital on the 9th of March, case two was the doctor who got it off the person who came in on the 9th," Health Minister Yvette D'Ath told reporters on Sunday.
"Case three is a person in hotel quarantine on the same floor as case one.
"We're assessing that at the moment. We've got CCTV footage .. to try to identify why this transmission might have occurred."
No guests will leave the hotel and no new guests will be checked into the site until the health officials have completed their investigation.
About 240 people linked to the infected doctor have been traced, with virus test results due back in the coming days, Deputy Chief Health Officer Sonya Bennett said.
Three close contacts of the doctor have all tested negative.
The infected doctor had contact with two patients in the early hours of Wednesday before testing positive on Friday.
One of the patients is likely to have passed on the highly contagious UK strain of the virus, although genomic testing was unable to confirm this, Dr Bennett said.
She said genomic testing also showed one of the patients was likely linked to the case being investigated at the Hotel Grand Chancellor, which was diagnosed on Saturday.
"They both travelled through the same area on the way," Dr Bennett said.
"The information is all a little bit unusual and what we want to rule out is that there's been any transmission in the hotel."
She said it was one of a number of explanations to explain the situation.
The female doctor worked a shift at PA late on Wednesday and Thursday while asymptomatic and was infectious in the community for about a day.
The hospital remains in lockdown and all hospitals, aged care and disability facilities in the Greater Brisbane area are closed to visitors and masks must be worn inside them.
