WINDSOR, Ont. - The Windsor hospital where a woman underwent an unnecessary mastectomy says it is horrified and saddened by the mistake, but is not accepting blame for the error at this point.

Dr. Art Kidd, who was chief of staff at the Hotel-Dieu Grace Hospital last fall when the procedure was mistakenly performed, says the doctor involved admits she misread the results of a needle biopsy that found the woman did not have cancer.

The hospital says Dr. Barbara Heartwell then went ahead with the mastectomy.

Kidd says the hospital has begun a comprehensive investigation and review of its procedures to confirm they were followed, as well as to look for ways to make sure it doesn't happen again.

Heartwell's pathology reports will be read by another physician until the hospital's investigation is completed.

Heartwell could not be reached for comment, but the hospital says so far it has not received any notice of legal action stemming from the incident.