From 2010 to 2013, the number of recorded heroin-related drug overdose deaths almost tripled, reaching 8,620 deaths in 2013, although public health officials assume the real number of deaths is much higher because heroin rapidly metabolizes into morphine and is difficult to detect. According to United States officials, possible reasons for that increase include an overall increase in the number of heroin users, batches of the drug with greater purity being sold in certain markets, an increase in new and inexperienced heroin users, including those using heroin to supplement or replace prescription opioids, and the presence of toxic substances such as fenta-nyl in the heroin consumed. In Canada and the United States, deaths related to fentanyl abuse have continued to increase, with many recreational drug users succumbing to overdoses after ingesting opioids (primarily counterfeit oxycodone) which they were unaware were fentanyl-laced.