Two-thirds of the 63,632 drug-related deaths in the U.S. in 2016 were tied to opioids, according to a report from the Centers for Disease Control and Prevention.

Released on March 29, the report analyzed data on the death rates for opioid overdoses from 31 states and the District of Columbia.

“Opioids were involved in 42,249 (66.4 percent) of drug overdose deaths (13.3 per 100,000 population) in 2016, representing a 27.9 percent rate increase from 2015,” the report said. “These increases primarily were driven by deaths involving synthetic opioids, for which the rate doubled from 2015 to 2016.”

Deaths related to opioid usage increased in 2016 across all categories (race, gender and age). Twenty of the 31 states analyzed saw an increase, with D.C. experiencing the highest increase (392.3 percent) from 2015 to 2016.

Since 1999, a total of 632,331 people have died in the U.S. from a drug overdose. More than half (351,630) were opioid overdoses.

“The first wave of opioid overdose deaths began in the 1990s and included prescription opioid deaths,” the report explained. “A second wave, which began in 2010, was characterized by heroin deaths. A third wave started in 2013, with deaths involving highly potent synthetic opioids, … Synthetic opioid-involved deaths in 2016 accounted for 30.5 percent of all drug overdose deaths and 45.9 percent of all opioid-involved deaths, with a 100 percent increase in the rate of these deaths compared with 2015.”

The full report is available here.