A cancer patient suffering the side effects of chemotherapy was placed in a Covid-19 ward at Mayo University Hospital, according to documents released under the Freedom of Information Act.
In details of a complaint lodged by a relative of the patient, it is claimed that the man, who is an oncology patient, arrived at A&E on May 1 and was admitted to a Covid-19 ward where there were five Covid-19 patients.
He had "arrived at the hospital as a very vulnerable patient with a very serious underlying illness and a compromised immune system". He was not displaying any Covid-19 symptoms.
The complainant alleges that the man was moved into an isolation ward later that evening. However, by that time he had already been "exposed to the coronavirus, unprotected, for an extended period of time".
On May 4, when the complaint was made, the man was in self-isolation back at home. His daughter, who accompanied him to the hospital and entered the Covid-19 ward, was also self-isolating. It is claimed that both the cancer patient and his daughter were not given any protective equipment for hours. Later they were given "basic masks".
The complaint states that the man's "safety, health and life is now at serious risk" due to a failure by the hospital to implement "the most basic safety protocols".
The complaint was sent to Mayo University Hospital (MUH) manager Catherine Donohoe as well as to the Department of Health, for the attention of chief medical officer Tony Holohan.
"It is important that he knows what is actually happening on the ground which is very distressing for the people concerned," wrote the complainant.
Correspondence shows that on May 5, Declan Whelan, from the Cancer Policy Unit in the Department of Health, asked the hospital for an update on the complaint as a "matter of urgency".
Concerns about segregation procedures at the hospital have been raised by local councillors and TDs in the Mayo area.
Previously, the Irish Independent reported that Jackie Carolan (79), of Ballymunnely, Bellacorick, Ballina, died in a "Covid bay" on the elderly care medicine ward at MUH on April 1.
He had been moved into the bay, where there were three other suspected Covid cases, from a stroke bay on the same ward the day before he died.
The issue of patient crossover between wards was also raised by a woman claiming to be a journalist during a Department of Health briefing on Covid-19 in May.
Last month, then health minister Simon Harris requested a report from HSE chief executive Paul Reid on the Covid-19 measures taken at MUH from the outset of the pandemic.
The details of the cancer patient complaint were outlined in a Freedom of Information request submitted by Aontú.
Aontú leader Peadar Tóibín told the Irish Independent that staff and former patients at MUH have been raising concerns and relaying their experiences for a number of months.
"The documents released to us under the Freedom of Information Act show that these concerns went all the way up the chain of command, through Mayo University Hospital, the HSE and all the way to the Department of Health," he said. "We now know that the department was aware of the situation the day before it was raised at a press briefing by a woman posing as a journalist".
Mr Tóibín called for an update on the progress of the report commissioned by Mr Harris.
The Saolta Hospitals Group said it cannot comment on individual cases when questioned about the details in the complaint.