A hospital drug shortage which could lead to the cancellation of surgeries appears to be much worse than Alberta health officials let on earlier this week.

On Tuesday, a senior health official said while work is underway on a contingency plan, Alberta Health Services had adequate supplies of the drugs for now.

But CBC News has obtained a leaked Alberta Health Services memo which paints a different picture. The memo, which was sent to doctors on Feb. 23, states that hospitals are already experiencing "significant outages" of these drugs.

A second memo sent on Thursday discussed how seven "significant" injectable drugs are now at "critical" levels.

On Friday, Health Minister Fred Horne said he wasn't aware of any critical shortages that could threaten patient safety or the quality of care.

"There may be some impact on elective surgeries and we certainly hope that's not going to be the case," he said. "But some people may be inconvenienced because of that."

Horne says as far as he knows the shortage affects about 40 drugs used in hospitals. But CBC has been told that the number is more than 100.

The shortage is a result of a decision by Quebec-based manufacturer Sandoz to stop making some painkillers, antibiotics and anesthetics while it improves standards at its plant in Boucherville.

The plant is undergoing the upgrade to address concerns raised by the U.S. Food and Drug Administration.

Alberta physicians believe the looming shortage could result in cancelled surgeries.

"Some of these things are very powerful injectable painkillers, for example," said Edmonton anaesthesiologist Dr. Douglas DuVal.

"And so you wouldn't want to have a surgical procedure — leaving aside what happens in the operating room —if you're going to have a couple days' worth of surgical pain afterwards."

The problem affects hospitals across Canada and DuVal says every province is scrambling to find back-up supplies.

The slow-down is expected to last from a year to 18 months.