Inside the fentanyl trade powering the world’s deadliest drug crisis

What started as prescription painkiller is now the cause of a public health emergency in the US and it could soon creep into Ireland. But where does it come from? Stephen Gibbs and Keiran Southern investigate

Last year, fentanyl killed more Americans aged between 18 and 49 than traffic accidents or guns.

It was a distinctive smell, similar to vinegar, seeping from the new-built home at the top of the hill that prompted a resident in Tijuana’s Lomas del Valle neighbourhood to make an anonymous call to the police in October last year.

A few nights later, three patrol cars were seen heading up the pot-holed road to the elevated dusty area, a 50-minute drive and a world away from the souvenir stores and tequila bars of Mexico’s main northern border city. Their target was a squat, grey building that seemed in a permanently stalled state of construction.