At least 14 people were killed and eight injured in a shooting late on Tuesday in a drug rehab centre in Mexico's northern state of Chihuahua, local police said.
The assailants entered the centre "Uniting Families" and opened fire at the people inside, Xinhua reported.
It is estimated that about 25 people were staying in the centre when the first responders arrived on the scene to help the injured.
Over a dozen police vehicles have been deployed around the centre and police officers were searching for the attackers in nearby areas.
The state of Chihuahua, which borders the US, has seen some of the worst violence in Mexico's decade-long war on drugs.