The flow of heroin, meth and other illegal drugs into the United States has slowed during the coronavirus pandemic, the acting administrator of the Drug Enforcement Administration told The Wall Street Journal. Supplies of meth have been hardest hit.

“What we’re really seeing right now are supply-chain disruptions of nearly all illicit drugs,” Uttam Dhillon said in an interview. The main causes of the slowdown are significant restrictions to cross-border traffic between the U.S. and Mexico, in addition to social distancing mandates, he said. “You’ve got traffickers who just can’t move as freely as they could before without being quite obvious that they’re moving,” he told the newspaper. Laundering cash has also become more difficult, he noted.

At a harm-reduction nonprofit in Washington, D.C., clients say dealers are cutting heroin and cocaine with fentanyl to stretch supplies.