At least 10 police officers and one civilian have been killed in the northwestern state of Sinaloa after they were ambushed by a group of heavily armed men, a law enforcement sourced and media reported. The officers belonged to a security detail of Francisco Cordova, Sinaloa\'s public security secretary, who was not traveling with his bodyguards at the time of the attack. According to the police source, who spoke on condition of anonymity, the attack occurred near the town of Guasave Friday, when the bodyguards were returning to the state capital from a political event in Los Mochis in several cars. Cordova was not with them because he took a helicopter ride back, the source said. Some 37,000 people have been killed since Mexico launched a massive military crackdown in December 2006 on powerful drug cartels, which have waged brutal turf wars with each other and repeatedly clashed with security forces. Sinaloa has been the site of a bloody confrontation among leading Mexican drug cartels feuding over lucrative narcotics supply routes leading to the United States.