VANCOUVER—An alarming rise in sudden infant deaths in British Columbia over the last six months has puzzled health officials and left them struggling to find answers.

From Jan. 1 to June 28, B.C. Coroners’ Service were called in to investigate 21 sudden infant deaths. Last year, there were only 16 such deaths in total.

The province’s chief coroner Lisa Lapointe said there’s no known reason why there would be so many sudden infant deaths in the first half of the year.

“We’re always running aggregate reviews to see if there are any trends that we need to make sure we get on top of,” said Lapointe. “This is an alarming rise in sudden infant deaths. My first thoughts were we needed to make people know this is happening.”

There are no specific causes for sudden infant deaths, but placing an infant on his or her back to sleep has been known for many years to reduce the risk of sudden infant death, according to the Canadian Foundation for the Study of Infant Deaths website.

Other risk factors cited by medical officials include tobacco smoke or putting the baby to sleep on unsafe surfaces such as a couch or waterbed.

The rise in numbers happened throughout the province and not just in one area. While it’s unlikely that the rise in SIDS is linked to a rise in birth numbers over the last six months, Lapointe said it is possible that the higher rates are attributable to higher birth rates.

Over the last five years, the provincial average is 21 sudden infant deaths annually.

B.C. has one of the country’s more robust tracking systems of infant deaths and has a child death review unit to investigate any child death. Not all jurisdictions in Canada keep track of sudden infant deaths numbers.

The investigations of the 21 cases so far this year found that sleep practices were a factor if half of those deaths. Noreen Agrey, executive director of the Saskatchewan Prevention Institute, said always placing a baby on its back, ensuring the baby is not overheated and providing a safe sleeping environment can reduce the risk.