Embattled Health Minister Mary Harney dramatically revealed last night she was kept in the dark about a major inquiry into hundreds of suspected cancer blunders.

The embarrassing admission will put further pressure on her to resign after a series of shocking revelations on what was described as a "black day" for the troubled health system.

At least 97 women who underwent ultrasound scans at Portlaoise General Hospital are to be recalled for further examination amid fears they were wrongly given the all-clear for breast cancer.

The details were only made public by senior Health Service Executive officials when they were questioned by Opposition politicians at an Oireachtas committee yesterday morning.

Shockingly, the Health Minister and the head of the HSE, Professor Brendan Drumm, knew nothing about the new inquiry until hours before the meeting.

Ms Harney only found out about the 97 women when it was revealed in a question and answer session at the meeting.

The startling revelation highlighted the gaping lack of communication within the health service. And the women who now face the possibility of being diagnosed with cancer will only be contacted today.

They are part of a group of 568 whose ultrasounds had to be re-checked.

Of these, 294 have been given the all-clear. Another 177 will be given an initial examination today to see if they -- like the 97 other women -- must also attend a clinic in Dublin for further tests.

After a day of strong criticism at the insensitive manner in which the news was broken, the minister admitted last night she only became aware of the details at the meeting yesterday, where she was quizzed on her running of the health service with Prof Drumm.

She said the inquiry only came to light after her officials were gathering information for a parliamentary question and she was notified along with Prof Drumm on Wednesday night.

The inquiry is the second probe at Portlaoise Hospital and follows a review of over 3,000 mammograms, which has revealed nine women were wrongly told they did not have breast cancer.

"We weren't aware. I wasn't aware. The department wasn't aware that there was any other review other than the Dr Ann O'Doherty review. The first time that I became aware there was due process underway was last night," Ms Harney said

Tests

She knew that Dr O'Doherty was conducting an examination of mammograms but not that a parallel review of ultrasound tests at the hospital by its surgeon Dr Peter Naughton was also underway.

"We were aware of the Dr Ann O'Doherty review. We weren't aware until last night there was a dual or parallel review being conducted by Mr (Peter) Naughton," she said.

" I only became aware of the detail of that when Mr John O'Brien outlined it to the committee. That was the first time I became aware 97 women were going to be called back for further diagnosis.

"Clearly I think there are issues around the communication of this matter but my main concern remains with the individual women and I want to make sure they are seen as quickly as possible.

"I have apologised on a number of occasions and I reiterate that apology this evening."

John O' Brien, head of the National Hospitals' Office, who delivered the news to the committee yesterday morning, conceded the women who are being recalled face the possibility of being diagnosed with cancer.

Asked if he knew the revelations he made were a bombshell he said: "We were at the committee today -- we had no choice. It would have been viewed as if we were trying to hide information.

"We wanted to deal with it in a way which avoided women having to through a lengthy process and being seen by a consultant and having to go to another centre for an ultrasound.We had to get them somewhere where it could be all done for them on the same day.

"I am advised the final 177 will be completed by tomorrow and it is probable some more cases will emerge from that. We are trying to get them a one stop shop and will try to arrange for a hospital in Dublin to get them seen quickly," he said.

Questioned on who was responsible for the suspect ultrasound results, he said the work would have been done by a number of specialists in the Portlaoise radiology department.

- Eilish O'Regan, Shane Hickey and Fionnan Sheahan