WASHINGTON — After a catastrophic increase in 2020, deaths from drug overdoses rose again to record-breaking levels in 2021, nearing 108,000, the result of an ever-worsening fentanyl crisis, according to preliminary data published Wednesday by the Centers for Disease Control and Prevention.

The increase of nearly 15% followed a much steeper rise of almost 30% in 2020, an unrelenting crisis that has consumed federal and state drug policy officials. Since the 1970s, the number of drug overdose deaths has increased every year except 2018.

A growing share of deaths continues to come from overdoses involving fentanyl, a class of potent synthetic opioids that are often mixed with other drugs, and methamphetamine, a synthetic stimulant.

State health officials battling an influx of both drugs said many of the deaths appeared to be the result of combining the two.

Drug overdoses, which long ago surged above the country’s peak deaths from AIDS, car crashes and guns, killed about one-quarter as many Americans last year as COVID-19.

Deaths involving synthetic opioids — largely fentanyl — rose to 71,000 from 58,000, while those associated with stimulants like methamphetamine, which has grown cheaper and more lethal in recent years, increased to 33,000 from 25,000. Because fentanyl is a white powder, it can be easily combined with other drugs, including opioids like heroin, and stimulants like meth and cocaine, and can be stamped into counterfeit pills for anti-anxiety drugs like Xanax. Such mixtures can prove lethal if drug users are unaware they are taking fentanyl or are unsure of the dose.

Deaths from both classes of drugs have been rising in recent years.

But there is growing evidence that mixing stimulants and opioids — into combinations known as “speedballs” and “goofballs” — is becoming more common too.

Dan Ciccarone, a professor of family and community medicine at the University of California, San Francisco, who studies drug markets, has just begun a multiyear study of the combination of opioids and meth.

“We’ve never seen a powerful opioid such as fentanyl being mixed with such a potent methamphetamine,” he said.

The numbers released Wednesday are considered provisional, and may change as the government reviews more death records. But they showed that a crisis that escalated sharply during the first year of the pandemic does not appear to be letting up.