MEXICO CITY (Reuters) - Fourteen people were shot dead on Tuesday night at a drug rehabilitation center in northern Mexico as part of a territory fight between two criminal gangs, a spokesman for the state attorney general s office said. The shooting took place in the Rosario neighborhood of the city of Chihuahua, the capital of the border state Chihuahua, and left 14 people dead and 8 injured, spokesman Carlos Huerta said on Wednesday.  We have an ongoing preliminary investigation wherein we believe it was an attack carried out by a criminal gang fighting for drug territory in the area,  Huerta said. The so-called Aztecas street gang attacked the rehab center where some members of rival group Los Mexicles, associated with the powerful Sinaloa cartel, were located, Huerta said. The two groups are wings of cartels fighting over drug distribution routes, particularly for crystal meth. Last year, some 23,000 people were killed in violent incidents in Mexico, the deadliest year since President Enrique Pena Nieto took office in late 2012. Since then, violence has grown as the country s powerful drug cartels have splintered and consolidated while fighting ruthlessly for control of lucrative smuggling routes in the United States. Some 1,444 people have been killed so far this year in Chihuahua state alone, Huerta said. 