Scotland's health secretary has apologised to the parents of two patients who died in the Royal Hospital for Children in Glasgow.
Jeane Freeman expressed her "deepest sympathies" to the families of Milly Main, 10, and a three-year-old boy.
The two children died three weeks apart in August 2017 at the hospital, which is part of the Queen Elizabeth University Hospital campus.
They had been treated on a ward which was affected by water contamination.
On Monday, NHS Greater Glasgow and Clyde (NHSGGC) apologised for the distress caused to parents.
In a statement to MSPs on Wednesday, Ms Freeman said: "To lose a loved one in any circumstances is hard, but I cannot begin to imagine the pain of losing a child in these circumstances - or the suffering and grief that will stay with them for the rest of their lives.
"I also want to apologise to them that they feel they have not had their questions answered.
"They are absolutely right to ask and pursue their questions, and they are entitled to have them answered and to receive the support they need."
The children's deaths emerged after Labour MSP Anas Sarwar was contacted by a whistleblower, and the health secretary said NHS employees must have the confidence to speak up when something is wrong.
Ms Freeman told MSPs: "There is no room in our health service for anyone to criticise whistleblowers, publicly or otherwise - or to put them in fear for the safety of their jobs.
"We need to recognise that whistleblowing is not something people who have dedicated their lives to health care, do lightly. It takes courage and they should be thanked."
Ms Freeman also told parliament she has asked the head of NHS Scotland to review whether any escalation of measures for the health board is required.
The five-stage NHS Board Performance Escalation Framework is the Scottish equivalent of special measures, which apply in England and Wales.
Labour's Monica Lennon asked the health secretary who the parents of sick children should put their trust in.
Ms Freeman replied: "They can place trust in me. I have compassion, I have empathy, and that is why I met with those families and have undertaken the work that I have done.
"I refute absolutely from Miss Lennon, or from anyone else, that I am careless or irresponsible on these matters - it could not be further from the truth. It may suit you [Ms Lennon] to make those points for other reasons but they are not true and I refute them absolutely."
Families 'completely unsatisfied'
Ms Lennon, Labour's health spokeswoman, later said: "The tragic deaths and infection scandals at the Queen Elizabeth University Hospital have been cloaked in secrecy for too long.
"Families and the wider public need to have full confidence in the health board and the cabinet secretary. That's why vague answers from Jeane Freeman are sorely disappointing."
Scottish Conservatives health spokesman Miles Briggs called on Ms Freeman to resign or be sacked.
He said: "At the heart of this scandal, we must never forget, are grieving families who are completely unsatisfied and think there has been a cover-up, and who can blame them?
"The SNP planned and built this hospital, and has presided over its first few years in operation - it can't just keep pointing the finger at everyone else. As the SNP health secretary, the buck stops with Jeane Freeman."
An independent review is examining water contamination and other problems at the Queen Elizabeth University Hospital campus.
On Tuesday Ms Freeman told MSPs on Holyrood's health committee it would publish its findings in the spring.
The health secretary said she expects a separate public inquiry, which will examine safety and wellbeing issues at the QEUH and the new children's hospital in Edinburgh, will also look at water contamination.
Milly Main died on 31 August while recovering from leukaemia treatment. Her mother said she was "100%" convinced her death was linked to water contamination issues.
NHSGGC has insisted it was impossible to determine the source of Milly's infection because there was no requirement to test the water supply at the time.
On Sunday police confirmed they had investigated the death of a three-year-old boy three weeks before Milly died. Police said they passed a report to the procurator fiscal.
NHSGGC said they had fully investigated and shared their findings with the boy's family but the child's mother later described the board's media statement as "highly inaccurate".
Last week a whistleblower revealed that a doctor-led review had identified 26 infections at RHC during 2017 which were potentially linked to contaminated water.
The £842m Queen Elizabeth University Hospital "super hospital" has faced a number of problems since it opened in 2015.
Two cancer wards at the adjoining children's hospital were closed last year amid concern about infections and investigation of water supply issues, with patients decanted to the adult hospital.
In January it emerged that two patients at the QEUH had died after contracting a fungal infection linked to pigeon droppings.