John Gerrard said it was still unknown if there was a common source for the fungus but indicated two types were found within heart transplant patients at the Prince Charles Hospital.
Four patients who underwent heart transplants have experienced Aspergillus fungal infections this year, while a fifth patient had an infection with Lomentospora, Dr Gerrard said.
Muhammad Hussain died after contracting a fungal infection.
Two men, Muhammad Hussain, 55, and 45-year-old Adam Retmock both died from the infection.
Dr Gerrard said it was important to understand patients undergoing heart transplants were very immunosuppressed and subject to infections.
He said the Aspergillus type was extremely common and could be found in any air conditioning unit.
Five patients were diagnosed with a fungal infection after elevated levels of mould were found in a storage area at the hospital's heart transplant unit.
Dr Gerrard said the area had been cleaned, equipment discarded and air sampling cleared.
Queensland Health said early investigations suggest there was no link between the deaths and the fungal infection in the hospital's storage area.
The investigation was ongoing but the contaminated area has been eliminated as a concern, Dr Gerrard said.
"Obviously we are concerned, that's why this investigation is being undertaken," he said.
"We are not trivialising this at all, we are concerned.
"A source may be identified or it's quite possible it will never be identified and that we will not see further cases.
A storage area at the Prince Charles Hospital's heart transplant unit had elevated levels of mould.
"I personally would be more than prepared to undergo a heart transplant at the Prince Charles Hospital. This is a world class unit."
Health Minister Shannon Fentiman told parliament earlier on Tuesday the transplant unit had been paused for a deep clean but was now "absolutely safe" and reopened last week.
But in question time on Tuesday, Opposition Leader David Crisafulli said Mr Retmock's family had told him the transplant patient found out the fungal outbreak could be potentially fatal whilst in hospital watching the TV news days before his death.
Ms Fentiman said it was "totally unacceptable" if that was true but had been assured by the heart transplant unit that they had spoken directly to every patient about the outbreak.
"If that has not happened then I want to again sincerely apologise to those families," she told parliament.
"I absolutely agree it is not good enough if a family found out via the news."
Ms Fentiman said Mr Retmock had suffered a range of complications unrelated to the fungal infection before his death.
Muskaan Hussain says her family is still searching for answers.
The daughter of Mr Hussain said her family was notified of the fungal cluster hours before it was aired in the media.
Muskaan Hussain said her family was still searching for answers about hospital procedures and why it took so long to notify affected families.
"Infection control procedures, what safeguards they have in place to prevent something like this happening and the fact that a cluster developed and eventually five people fell ill," she said on Tuesday.
Of the three remaining heart transplant patients with fungal infections, two are recovering at home while the other is in hospital with an unrelated clinical issue.
Clinical reviews of both deaths were ongoing, the minister said.
30°C