At least 46 surgeries have been called off within 24 hours as technicians worked to investigate a substance found on the packaging of sterilised surgical tools.

Key points: Both Dr Playford and the Health Minister confirmed no patients were exposed to unsterilised equipment

Both Dr Playford and the Health Minister confirmed no patients were exposed to unsterilised equipment The problems prompted 46 surgical procedures to be postponed within 24 hours

The problems prompted 46 surgical procedures to be postponed within 24 hours Some surgery is still being carried out, but elective procedures are being rescheduled

The hospital's infection control director Geoffrey Playford said equipment was sterile, but the residue of an unknown chemical had been discovered on the packaging of equipment.

"Our investigation has revealed that a change to the chemical added to the steam boilers, which is safe, improves the quality of the steam by altering things like the pH and oxygenation of the steam, is leaving a residue on the wrapping of those sterile packs," Dr Playford said.

"We can confirm the instruments are sterile, we have tested them over and over, we are working to remove the chemical residue from the steam lines now.

"As always, patient safety is our priority and we can confirm that no patients have been exposed to unsterilised equipment."

Dr Playford confirmed "some emergency surgical procedures" were being performed using reserve sterilised equipment.

"We have a number of packs that have been sterilised here that are unaffected by that process and we are working with other facilities in the Metro South [region] and the RBWH who have been very kind enough to help us process those instruments at their facilities," he said.

"We'll be able to rapidly resterilise [and] process all our packs over the weekend."

Patient's surgery cancelled minutes before it starts

A Brisbane woman — who did not want to be identified — was only five minutes away from receiving major shoulder surgery on Thursday when she was told her operation had to be cancelled.

"When he [the surgeon] said 'we can't do it at all', my husband just stared at [me] and [I] just stared at him because it was unbelievable," she said.

"I think I spent most of last night in tears.

"The reason they gave me was the sanitary system hadn't cleaned, or hadn't sterilised the instruments and the implants that were to go into my body, and for them to re-sterilise them would take another four to six hours.

"I honestly couldn't believe that I was in that situation."

The woman said she was still waiting to find out when her surgery would take place.

Dr Playford apologised to patients.

"We regret very much having to reschedule elective surgical procedures — we understand that has a very large impact on patients and their family.

"In the end we had no option but to do that, as it is the safety of our patients that comes first."

The Health Minister said technicians were trying to fix problems at the hospital. ( ABC News: Stefan Lowe )

Authorities unable to identify residue

Hospital staff told ABC News they noticed rust on the equipment earlier this week.

Dr Playford said while authorities are still investigating the compound of the chemical left on the packaging of the surgery tools, they do not believe it is rust.

"As a result of that investigation, we have found through flushing or purging of the steam lines we can eliminate this chemical residue — this is expected to happen over the weekend and sterilisation facility will be back to normal by Monday," he said.

"It is important to realise that this does not indicate any breach of the sterility process — all the surgical instruments used passed all their standard microbial sterility testing.

"This is not a rust or degradation of the surgical instruments — this is a chemical residue."

Earlier, Health Minister Steven Miles said elective surgeries were being rescheduled.

"Due to a malfunction with the sterilisation equipment, the Princess Alexandra Hospital is only conducting emergency and urgent elective surgery today with reserve sterilised equipment," he said.

On Thursday night, a spokeswoman for the Metro South Hospital and Health Service confirmed the issue to ABC News, saying the hospital was "not currently conducting surgeries".

Opposition health spokeswoman Ros Bates said the public deserved to know what had gone wrong.

"Certainly when you're sterilising equipment for theatre — and I have been a theatre nurse in the past — you need to be absolutely sure the equipment you have used, and the reports you have generated from the sterilised equipment, is accurate and that the instruments that you're about to put inside a patient are sterile," she said.

"Sterilised equipment should be checked regularly — it should be serviced and maintained regularly.

"If that's not the case, then that's put patients at risk of serious post-operative infections."