A new study finds that opioids were responsible for more than half of all fatal poisonings in children under age 5 in 2018. The rate of fatal opioid poisonings in young children has doubled since 2005, CNN reports.

The researchers evaluated child death review data from the U.S. National Center for Fatality Review and Prevention. Of the poisoning cases in which the circumstances were documented, more than 40% of deaths were accidental overdoses, the researchers found. Almost 18% were considered deliberate poisonings.

The researchers said that while child-resistant packaging for many medicines and hazardous products has greatly reduced the number of unintentional fatal poisonings in young children, the growing opioid epidemic in the United States has contributed to recent child poisoning deaths.

“By comprehensively assessing fatal poisonings among children at a national level, we were able to better understand the scale of this tragic and preventable public health issue,” first study author Christopher Gaw, M.D., of the Children’s Hospital of Philadelphia said in a news release. “We were also able to specifically characterize the proportion of poisoning deaths that could be attributed to opioids each year.”