CELAYA, July 4 -- Mexican rehabilitation centers were supposed to provide sanctuary to drug users trying to kick their addictions. Instead, they became targets for the same ultra-violent cartels that traffic illegal narcotics.

The refuges are reeling from a series of deadly attacks by criminal gangs fighting for control of the multibillion-dollar drugs trade, particularly in Guanajuato, Mexico's most violent state.

Some of the people in rehab are pursued by drug dealers whom they owe money, Nicolas Perez, who leads a network of 180 rehabilitation centers in Guanajuato, told AFP.

Perez, 55, said he had himself received calls from suspected criminals demanding he hand over some of the addicts at the centers he oversees.

Instead, he cont...