Ambulance workers in Ciudad Juarez, Mexico's most violent city, are under constant threat as drug gangs battle each other for territory.

The situation has grown so dangerous that paramedics have been ordered to wait for police to arrive at a crime scene before attending a call.

Gunmen have even been known to follow wounded patients from ambulances to emergency rooms to finish them off.

Al Jazeera's Mariana Sanchez has the story from Ciudad Juarez, in the first of a series of special reports on the drugs war.