OTTAWA -- Canada's opioid crisis claimed the lives of more than 11,500 people between January 2016 and December 2018, the Public Health Agency of Canada reported Thursday.

New data shows that 4,460 people died in 2018 alone and many of these deaths were related to the contamination of the illegal drug supply, the agency said.

The federal health agency said an analysis of national trends suggests there was a significant increase in death rates between January 2016 and June 2017, noting the rates then stayed high from July 2017 to December 2018.

It also said Western Canada remains the most affected region of the country.

The epidemic remains the most challenging public-health crisis in decades, said the co-chairs of federal government's advisory committee on the epidemic of opioid overdoses, chief public-health officer Dr. Theresa Tam and Saskatchewan chief medical-health officer Dr. Saqib Shahab.

Fentanyl and other fentanyl-related substances continue to be a major driver of the crisis, they added.

Fentanyl is an opioid more potent than heroin or morphine, often cut with fillers and then passed off as its less-powerful cousins because it's easier to transport and hide. People who use illegal drugs often can't know exactly what they've bought and a tiny excess dose can be fatal.

"There is still much work to be done to abate the opioid crisis, and Canadians can be assured that addressing it remains our priority," Tam and Shahab said in a joint statement.

Numbers on opioid overdoses take a long time to extract from sources like hospital records because they aren't always tracked in easily comparable ways and people who suffer them often have other serious health problems. It's only now, almost halfway into 2019, that the public-health agency has been able to compile figures through to the end of last year.

Even so, the 11,577 deaths since January 2016 are qualified as "apparent opioid-related overdoses." According to the health agency, most of the people who have died also had other potentially harmful substances in their systems, such as alcohol, cocaine or methamphetamines.

As the death toll climbs, the federal government has faced pressure from health advocates to allow for a safe supply of opioids to be made available to people suffering from addiction so they do not have to turn to a toxic street supply.

There has also been a push to decriminalize simple possession, including by Liberal MP Nathaniel Erskine-Smith, who is putting forward a private member's bill proposing the removal of penalties for simple possession of drugs from the Controlled Drugs and Substances Act.

Earlier this week, the House of Commons health committee issued a report urging the federal government to look at Portugal's decriminalization of simple possession and examine how the idea could be "positively applied in Canada."

It made the recommendation, among others, in a report produced after committee members travelled across Canada to witness the impacts of methamphetamine use.

Witnesses who appeared before the committee called for the federal government to work with provinces, territories, municipalities, Indigenous communities and law-enforcement agencies to decriminalize simple possession of small quantities of illicit substances, the report said.

The Conservatives on the health committee issued a dissenting report saying that several other things need to be done before decriminalization, pointing out a number of differences between Canada and Portugal. They say Canada needs better drug-treatment programs and more public education about drugs.