Unintentional fatal drug overdoses in the United States nearly doubled from 1999 to 2004, overtaking falls to become the nation’s second-leading cause of accidental death, behind automobile crashes, the government reported.

The number of accidental drug overdose deaths rose from 11,155 in 1999 to 19,838 in 2004, according to the U.S. Centers for Disease Control and Prevention.

The report was based on death certificates, which do not clearly detail which drugs played the greatest role. But CDC researchers said they believe sedatives and prescription painkillers like Vicodin and OxyContin were the chief cause of the increase.

OxyContin has been blamed for hundreds of deaths across the country in recent years.

Deaths from falls climbed between 1999 and 2004 at a more modest rate, from 13,162 to 18,807, the CDC said. Motor vehicle crashes accounted for 40,965 fatalities in 1999 and 43,432 in 2004.

The South had one of the lowest fatal drug overdose rates in the nation in 1999, but it doubled by 2004. The South now ties the West for having the highest rate — about 8 per 100,000 population.

“This is the first study really to describe the large relative increases in poisoning mortality rates in rural states. Historically, the drug issue has been seen as an urban problem,” said Dr. Len Paulozzi, a CDC epidemiologist.

The federal report, issued this week, noted that accidental drug overdoses remain most common in men and in people 35 to 54. But the most dramatic increases in death rates were for white females, young adults and Southerners

Other findings:

— The death rate for men remained roughly twice the rate for women, but the female rate doubled from 1999 to 2004 while the male rate increased by 47 percent.

— The rate for white women rose more dramatically than for any other gender group, to 5 deaths per 100,000 population.

— The rate of overdose deaths among teens and young adults, ages 15 to 24, is less than half that of the 35-to-54 group. But it rose much more dramatically, climbing 113 percent in the study years, to 5.3 deaths per 100,000 population.

About 50 percent of the deaths in 2004 were attributed to narcotics and hallucinogens, a category that includes heroin, cocaine and prescription painkillers like Vicodin and OxyContin.

“There is a misperception that because a drug is a prescription medicine, it’s safe to use for non-medical reasons. And clearly that is not true,” said Dr. Anne Marie McKenzie-Brown, a pain medicine expert at Atlanta’s Emory Crawford Long Hospital.