It has emerged that thousands of drug addicts live in the shadows of Ciudad Juarez, the infamous Mexican border city at the epicenter of a wave of brutal drug violence as well as growing drug use.
Abandoned by authorities, the addicts live in fear of drug gangs who threaten and sometimes kill them for no apparent reason, including several brutal massacres in drug treatment centers.
"Now they enter houses and kill us. We keep this window open so we can at least try to escape over the roof," said a drug user who gave her name as Carla, inside a house used as a 'shooting gallery' for heroin in Barrio Alto, a central district dotted with abandoned businesses.
Groups of addicts huddle in hundreds of similar spots of desolation in the border city across from El Paso, Texas, from which thousands of wealthier residents have fled in recent years.
The city government counts more than 5,000 heroin addicts alone in Ciudad Juarez, the largest group in Latin America.
Many openly shoot up, like Ricardo, who sits on the back of a pick up truck next to the factory which employs him as a security guard.
A trail of users visit the truck during the day, sometimes aided by another addict to inject themselves.
Ricardo said he did not charge people to use his space but asked them to cooperate.
"You have to be discreet and avoid the drug trafficking circuit. I don't sell, you need to ask the gangs permission for that. Even without selling it's become very dangerous," Ricardo said hurriedly.
Like the authorities, Ricardo blames the wave of killings in the city -- some 6,500 in three years -- on a move by the powerful Sinaloa drug cartel to take over gangs dominated by the Juarez cartel.
More than 28,000 people have been killed in rising suspected drug violence across the country since 2006, according to official figures.
Health activists visit the Ciudad Juarez drug addicts daily to change or clean their needles.
The addicts sometimes tell them of others who have been killed for unknown reasons.
Mexican President Felipe Calderon -- who launched a controversial military clampdown on drug gangs in 2006 -- also blames the growing violence on the thirst of the gangs to supply a growing local market.
Activists and health workers say the government has failed to show the same commitment to tackling drug use as it has to deploying thousands of troops across the country.
"They promised help and resources but we're still waiting for them," said Jose Antonio Rivera, director of the public, autonomous, Center for Youth Integration.
A first public detoxification clinic has just opened, with 30 beds, while most addicts who seek treatment attend private clinics, some with public funding.
But these centers have also been targeted by drug traffickers in brutal massacres, which have left at least 47 dead in three such attacks in the past year alone.
These only contribute to the city's growing climate of fear.
"Sometimes I realize that my mother watches me when I wash cars in the street," Carla said.
"With the situation as it is, it's enough for her to know I'm still alive."