The number of deaths in the United States involving heroin more than tripled between 2010 and 2014, according to a new report by the Drug Enforcement Administration (DEA). The number of people reporting current heroin use nearly tripled between 2007 and 2014, the agency said.

The DEA’s 2016 National Heroin Threat Assessment Summary found 425,000 people said they used heroin in the past month in 2014, and 10,574 people died from the drug. Deaths due to synthetic opioids, such as fentanyl and similar drugs, increased 79 percent between 2013 and 2014.

Many people who use prescription opioid painkillers become addicted, and then switch to heroin because it is cheaper and easier to obtain than illegal prescription drugs, the DEA noted.

The rise in heroin deaths may be partly due to an increase in people who are new to the drug and inexperienced in its use, ABC News reports. Highly toxic adulterants such as fentanyl, which is being mixed into heroin in certain markets, also plays a role, the DEA stated.

The heroin threat is greatest in the Northeast and Midwest. Mexican drug traffickers have gained a larger share of the biggest heroin markets in the United States, including Baltimore, Boston, Chicago, New York, Philadelphia and Washington, D.C., the report found. Traffickers also moved their operations into suburban and rural areas.

“We tend to overuse words such as ‘unprecedented’ and ‘horrific,’ but the death and destruction connected to heroin and opioids is indeed unprecedented and horrific,” DEA Acting Administrator Chuck Rosenberg said in a news release. “The problem is enormous and growing, and all of our citizens need to wake up to these facts.”

Earlier this week, the United Nations Office on Drugs and Crime released a report that estimates one million people used heroin in the United States in 2014, almost triple the 2003 rate. Heroin-related deaths have increased five-fold since 2000, the World Drug Report 2016 found.