Rhodri Morgan, with his MP wife Julie, leaving the University Hospital

A patient is believed to have threatened staff at Cardiff's University Hospital with a sharp object, sparking a police operation.

At the time Mr Morgan, 67, was being treated for two partially-blocked arteries.

Cardiff and Vale NHS Trust confirmed there was an incident on 10 July.

Mr Morgan had been admitted to Llandough Hospital in Penarth on Sunday, 8 July, suffering from what was described as gastric problems.

After spending the night there, he was transferred to the University Hospital of Wales for an angiogram.

As a result the first minister was treated with stents for two partially-blocked arteries.

While he was recovering on the cardiac ward, BBC Wales understands a patient from the intensive care unit became distressed and broke a window using a chair.

Staff in the area reacted to the incident immediately to ensure the safety of the patients Cardiff and Vale NHS Trust

It is believed he then threatened staff with a shard of glass from the window.

He then made his way from the intensive care unit to the cardiac care unit as police and hospital security were alerted by hospital staff.

Mr Morgan was woken during the incident. It is understood he was on a general cardiac ward with other patients, and was not receiving any special treatment as a result of his status.

Hospital sources have also stressed that their response to the incident was exactly as it would have been whether he was a patient or not.

It is also understood there were no security precautions taken at the hospital as a result of Mr Morgan's presence and there was no suggestion either that the incident was linked to him being there.

Mr Morgan told the BBC through his spokesperson that he was full of admiration for the staff and their professionalism in dealing with the incident.

In a statement, the trust said that "staff in the area reacted to the incident immediately to ensure the safety of the patients".

"The trust is now investigating the circumstances and will act upon any recommendations that are identified," the statement added.

However, the trust declined to confirm whether a shard of glass was used in the incident.

After his treatment, Mr Morgan had said he was full of admiration for the staff.

"I was a huge admirer of the NHS before. I am an even greater admirer of the NHS now," he said after leaving hospital on 11 July.

Staff working in the NHS in Wales are subjected to an average of 22 cases of violent or aggressive behaviour every day, according to a study.

During the financial year 2005-06 there were nearly 7,800 reported violent or aggressive incidents against employees working in the NHS in Wales.