Prescription drug abuse continues to be the nation’s fastest growing drug problem, according to a new report by the Drug Enforcement Administration (DEA). Americans are abusing prescription drugs at a higher prevalence rate than any illicit drug except marijuana.

Pain relievers are the most commonly abused prescription drugs, and are most likely to be involved in overdose incidents, the article notes. Last year, 28 percent of law enforcement officials said prescription drugs are their biggest drug problem, up from 9 percent in 2009.

Heroin was easier to obtain in the United States last year, likely due to high levels of heroin production in Mexico, and Mexican traffickers expanding into white powder heroin markets in the eastern and Midwestern United States, the DEA said. Many prescription opioid users have turned to heroin because it is cheaper and/or easier to obtain, law enforcement and treatment officials around the country report.

Cocaine was less available in some parts of the country, the Miami Herald reports. Several major cities, including Chicago, Houston, St. Louis, Phoenix and Baltimore, reported sporadic interruptions in cocaine availability in the spring of 2012. These interruptions may have been due to counterdrug efforts, conflict within and between drug cartels in Mexico, and continued reductions in cocaine production rates in Colombia.

The availability of methamphetamine and marijuana is likely on the rise because of increased production in Mexico, and ongoing domestic production, the DEA noted. The agency is also concerned with the abuse of synthetic drugs, such as K2, Spice and bath salts.