In a statement security officials in the city of Chihuahua said "an armed group entered the Uniting Families rehabilitation center," attacking those inside with assault rifles.
First responders arrived on scene to care for the wounded in the center, where some 25 people were estimated to have been during the attack.
The state of Chihuahua, which borders the United States, has endured some of the worst violence in Mexico's decade-long militarised battle against drug trafficking.
Since the Mexican government launched its war on cartels in 2006, more than 200,000 people have died or disappeared amid the violence.