Dozens of non-urgent surgeries were postponed or cancelled across Quebec on Thursday after the provincial blood bank revealed concerns about the possible contamination of up to half its stock.

Héma-Québec initially said it may have to quarantine up to 70 per cent of its blood supplies, but it reassessed the situation later in the day and said nearly half of its shelved blood will have to be examined.

The blood was quarantined owing to concerns about small cracks found in the bags used to collect it.

According to Montreal's public health authority, about 10 heart surgeries in total were delayed at the Centre Hospitalier de l'Université de Montréal, the McGill University Health Centre and the Montreal Heart Institute. Ten other procedures were delayed or cancelled at St. Mary's Hospital and Santa Cabrini Hospital.

No firm numbers were given as to how many surgeries were affected in each hospital.

Laurent-Paul Ménard, director of external communications for Héma-Québec, said there was a problem with the bags used to collect the blood. The small leaks, or microcracks, which were found in some bags could be from a manufacturing defect, the agency said.

Ménard said the blood, some of which has already been distributed to hospitals, risks being exposed to the air. Air exposure could create favourable conditions for bacterial growth.

The temporary quarantine is a preventive measure, and Ménard said the agency is still able to respond to urgent needs. Emergency surgeries will still be performed and trauma centres will be able to respond to demands.

"Héma-Québec has the reserves necessary to fulfil the needs of the hospitals, except for some remote areas," Quebec Health Minister Réjean Hébert said Thursday. Surgeries were delayed in some remote areas, he said, to ensure their blood inventory was still full.

The Montreal public health authority confirmed all 17 hospitals in Montreal were warned about the blood supply problem.

The authority said health centres that have had to quarantine part of their blood supplies have blood reserves for the next two to three days. They normally have reserves for up to eight days of normal operating.

Testing on quarantined blood underway

Héma-Québec said Thursday that tests are being carried out on the quarantined blood. Blood thtat's found to be safe will eventually be recirculated.

Radio-Canada reported that the situation has forced the cancellation of surgeries at the Chicoutimi Hospital and the Alma Hospital, both in Quebec's Saguenay-Lac-Saint-Jean region.

Ménard did not say how many other hospitals in Quebec could be affected.

Blood products not quarantined and currently available for transfusion are safe, according to Héma-Québec. The agency also assured there is no risk to anyone who recently received a blood transfusion.

With files from The Canadian Press