Illegal drug seizures decreased sharply in the United States in the first two months of the COVID-19 lockdown, but rose quickly once stay-at-home orders were lifted, a new study finds.

Researchers at New York University studied seizures of marijuana, cocaine, methamphetamine, heroin and fentanyl in five locations between March 2019 and September 2020, HealthDay reports.

During that period, law enforcement officers made more than 29,500 drug seizures. They declined sharply in March and April 2020, but rose through the rest of the spring and summer. Marijuana and methamphetamine seizures declined the most during the early days of the pandemic.

“At the beginning of the pandemic, it was unclear how social distancing, travel restrictions and economic hardship in communities would impact drug supply and demand,” Nora D. Volkow, M.D., director of the National Institute on Drug Abuse, said in a news release. “Drug seizure data like these give us additional insight into the changing drug use landscape during COVID-19 and may inform our understanding of rising rates of methamphetamine- and opioid-involved overdose deaths during the pandemic.”