From Mexico cartel safe house to US streets: BBC tracks deadly fentanyl targeted by Trump tariffs

The fentanyl dealer from Los Angeles stands to the side watching carefully as a Mexican drugs cartel operative prepares his latest shipment. The synthetic opioid drug is wrapped in foil, sealed in plastic, then dropped with an oily splash into the petrol tank of the trafficker's nondescript car.

Jay, not his real name, had crossed earlier from the US to this cartel-run safe house on the Mexican side of the border. The house looks like any other in this neighbourhood. We are told to drive in quickly and an iron gate closes firmly behind us. They don't cook the drug here, but still they are wary of attracting attention. The men all speak in hushed voices and work quickly.