Health Canada says it has received reports of at least 23 young Canadian women who have died while taking one of two commonly prescribed birth control pills, Yaz and Yasmin.

More than half the reported deaths were in women younger than 26, including one who was 14.

The agency reports it has received 15 reports of deaths among women taking Yasmin up to the end of February. It has received eight reports of deaths among women taking Yaz.

Most of the deaths occurred soon after the women started taking the pills. Some involved pulmonary embolisms, meaning blood clots that had travelled to the lungs. Others appeared to have died of heart attacks or cerebral thrombosis, meaning blood clots in the brain.

Health Canada says it is not able to determine if any of the deaths were a direct result of using a specific health product.

“Other factors contributing to the (adverse reaction) could be a person's health conditions or other health products they are using at the same time,” the agency said in an email to CTV News.

Health Canada says it’s also received reports of about 333 cases of “adverse reactions” from women taking Yasmin and 267 cases involving Yaz up to the end of February. These included fainting spells, non-fatal pulmonary embolisms and blood clots in the legs.

Some of the women were taking other medications at the time of their adverse events, such as asthma or ADHD medications, while others were taking the birth control pills alone.

In an email statement to CTV News, Bayer, the maker of Yaz and Yasmin, said it is aware of the reports of deaths but “fully stands behind Yaz and Yasmin.”

The company said it exchanges information with Health Canada on all reported adverse events on a monthly basis.

“At Bayer we take the safety of our products very seriously and we continuously review the safety profiles of our products worldwide,” the statement said.

“Bayer investigates reports on side effects thoroughly and collaborates closely with Health Canada concerning the use, benefits and risks of all products, including Yaz and Yasmin. Bayer strongly encourages all patients and healthcare professionals to report adverse events to the company directly or to Health Canada.”

The company said its own data as well as independent research show the two products are “safe, effective and have a favourable benefit-risk profile” when used as directed by Health Canada.

In a second statement to CTV News, the federal agency said: “At this time, it is Health Canada’s view that the benefits of Yaz and Yasmin continue to outweigh the risks, when used according to Health Canada’s approved labelling instructions.”

The statement added that a decision to withdraw a product from the market is never taken lightly.

“Health Canada’s approach to drug withdrawal is based on scientific evidence and evaluation of the health risk to the Canadian public. When the benefits associated with a product are determined to no longer outweigh its risks, the decision may be made to withdraw the product from the market.”

Health Canada has been reviewing the safety of Yaz and Yasmin since 2011, after published studies suggested the pills appeared to raise women's risk of blood clots more than other birth control pills.

Blood clots have long been a well-known, though rare, side effect for all birth control pills. A Health Canada review released at the end of 2011 reported that women using Yasmin and Yaz had a 1.5 to three times higher risk of blood clots than women on other oral contraceptives.

Yasmin and Yaz are similar to other contraceptive pills but contain a hormone called drospirenone. It replaces the hormone levonorgestrel used in other types of birth control pills.

In April, 2012, the U.S. Food and Drug Administration ordered Bayer to change its U.S. labelling to note the increased risk for blood clots.

A class-action lawsuit involving several hundred women in Canada who used Yaz and Yasmin was launched in 2010, and certified in Ontario last April. It is one of several such class actions that have been filed across the country.