PORTLAND, Maine (AP) The number of drug overdose deaths in Maine increased by nearly a quarter in 2021.

An estimated 636 people died of overdoses last year, up 23 percent from the previous year, the Portland Press Herald reported. Researchers informed Maine lawmakers this week that the growing number of deaths is related to fentanyl being laced into other drugs without the knowledge of the user.

University of Maine researcher Marcella Sorg told lawmakers the trend in Maine reflects a growing problem nationally. The U.S. Centers for Disease Control and Prevention has estimated there were about 101,000 overdose deaths for the year-long period that ended in June. That was an increase of more than a fifth from the previous year.

The pandemic has worsened the crisis, Sorg said. More people are using the drugs alone, which means no one is able to administer naloxone, she said.