NEW YORK — U.S. overdose deaths last year likely fell for the first time in nearly three decades, preliminary numbers suggest.

The Centers for Disease Control and Prevention on Wednesday posted data showing nearly 68,000 drug overdose deaths were reported last year. The number may go up as more investigations are completed, but the agency expects the tally will end up below 69,000.

Overdose deaths had been climbing each year since 1990, topping 70,000 in 2017.

The numbers were celebrated by the U.S. secretary of health and human services. “Lives are being saved, and we’re beginning to win the fight against this crisis,” Alex Azar wrote in a tweet.

But the overdose death rate is still about seven times higher than it was a generation ago.

“We’re still in a pretty sad situation that we need to address,” said Rebecca Haffajee, a University of Michigan researcher.

Researchers do not believe this is the start of a dramatic decline. Data from the first months of this year likely will show that the decrease is not gaining steam, said Farida Ahmad of the CDC’s National Center for Health Statistics.

The improvement was driven by a drop in deaths from heroin and prescription painkillers. Those falls were offset somewhat by an increase in deaths involving a different opioid, fentanyl, as well as other drugs such cocaine and methamphetamines. Overdose deaths often involve more than one drug.

The improvement is not uniform: Some states seem to be making dramatic progress, while deaths continue to rise in others. The preliminary CDC data suggested deaths last year were down by as many as 1,000 or more in Ohio and Pennsylvania — each seeing declines of about 20 percent. Meanwhile, deaths increased by about 17 percent in Missouri.