A hospital has been forced to postpone heart and lung operations after surgical instruments became contaminated.

The problem at Sheffield's Northern General Hospital is thought to have been caused when a lubricant reacted with a new instrument cleansing machine.

Twelve patients had operations postponed, but the hospital is stressing there were no "clinical incidents".

Sheffield Teaching Hospitals NHS Trust spokesman Chris Horner said: "We have unfortunately been forced to postpone a number of cardiothoracic operations over the last week.

'Patient safety'

"Tiny particles were found on a few surgical instruments following the sterilisation process.

"All other theatre sessions have not been affected and are going ahead as planned.

"Each set of instruments is stringently inspected before being put into use and in the interests of patient safety.

"We have no choice but to postpone an operation if there is even the smallest doubt."

Small flakes were discovered on the instruments during the routine checks.

Mr Horner added: "We apologise sincerely to the patients who have had their operations affected, and we are now aiming to get back to normal business at the beginning of next week."