The Health Service Executive has said it has extended a review of colonoscopies carried out at Wexford General Hospital, which was originally announced in February, as a precautionary measure.
The review relates to one consultant at the hospital and screening and diagnostic colonoscopies carried out in 2013 and 2014.
A further 330 reviews are taking place, in addition to 281 already conducted.
A colonoscopy involves an examination of the bowel to look for abnormalities.
The additional 330 patients have been notified and appointments are being set up.
The HSE says the extension is an extra precaution to ensure all patients have had a colonoscopy of the highest quality.
Of the extra 330 patients being called for a repeat procedure, 210 previously underwent a screening colonoscopy under the BowelScreen programme.
A further 121 patients who previously underwent a diagnostic colonoscopy have been recalled for an outpatient appointment.
The HSE has said a small number of these may require a colonoscopy and so far 30 patients have attended for their appointment.
The HSE says that all patients have been contacted and an information line remains open at Callsave 1850-241850 for anyone with queries or concerns.
The review started because the HSE's BowelScreen programme and Wexford General raised concerns about the quality of screening procedures, after two patients in October and November 2014 were identified with interval cancers, a cancer that is detected between bowel screenings.
Ken Mealy, consultant surgeon at Wexford General, has said that the HSE is proceeding on the basis that some bowel cancers may have been missed at the initial colonoscopy but he could not say that yet with certainty.
Speaking on RTÉ’s Today with Sean O' Rourke, he said that when the review process is complete, the HSE will be able to speak about any cancers that may have been missed.
He said that one of the problems was whether a cancer might have been missed, or if it had grown since the initial test, and experts may disagree on this matter.
Mr Mealy insisted that the HSE was committed to open disclosure in relation to the total of over 600 patients concerned.
This issue is separate to the review of x-rays and other scans involving three locum consultant radiologists that was reported yesterday.