The Biden administration took aim Tuesday at the fentanyl trafficking threat, announcing a series of indictments and sanctions against Chinese companies and executives blamed for importing the chemicals used to make the deadly drug.

Officials described the actions, which include charges against eight Chinese companies accused of advertising, manufacturing and distributing precursor chemicals for synthetic opioids like fentanyl, as the latest effort in their fight against the deadliest overdose crisis in U.S. history. The moves come one day before senior administration officials are set to visit Mexico, whose cartels are part of the global trafficking network, for meetings expected to involve discussion of the drug threat.

“We know that this network includes the cartels’ leaders, their drug traffickers, their money launderers, their clandestine lab operators, their security forces, their weapons suppliers, and their chemical suppliers,” Attorney General Merrick Garland said at a news conference. “And we know that this global fentanyl supply chain, which ends with the deaths of Americans, often starts with chemical companies in China.”