Twenty-two suspected Zetas drug gang members have been held in the latest arrests over the killings of 145 people found in mass graves this month in northeast Mexico, the justice ministry has said.he arrests brought the total to 55 detained, including 16 police officers and a suspected ringleader, for alleged involvement with the mass graves found in San Fernando, Tamaulipas state, near the US border. Marines detained the 22 latest suspects, including five women, in an operation Friday. They were accused of involvement in organized crime, murder, kidnapping and violating firearms laws, a statement said. A total of 145 bodies have now been unearthed from mass graves in San Fernando, which lies on a path regularly used by migrants heading for the United States. Tamaulipas state has suffered an explosion of violence for more than a year blamed on battles between the Zetas -- a gang formed in the 1990s by ex-elite soldiers -- and their former bosses, the powerful Gulf cartel. Authorities also blame the Zetas for the massacre of 72 migrants in Tamaulipas last August. More than 34,600 people have died in Mexican drug violence since 2006, according to official figures, amid a widespread military crackdown on organized crime. Ten outlaws died in a shootout with soldiers Tuesday in the eastern port city of Veracruz, where the Zetas and Gulf gangs are also fighting for turf, local authorities said in a statement.