New York: Human Rights Watch called on Mexico to conduct an "independent" probe into the June killing of 22 civilians by soldiers in the town of Tlatlaya. Twenty-one men and a woman were killed when soldiers returned fire after they were targeted by armed assailants guarding a warehouse, Mexico`s defense ministry said on June 30. However "there are more questions than answers about what really took place that day," said Jose Miguel Vivanco, Americas director at Human Rights Watch. "A thorough, objective, and independent investigation that examines whether the soldiers acted lawfully, and assesses evidence of state misconduct is needed and required by law," Vivanco said yesterday. According to HRW, "credible reports regarding the forensic evidence at the scene of the shooting suggest that the soldiers used excessive force." The fact "that the soldiers killed all 22 suspects and sustained only one injury raises questions about whether the use of force was proportional," Vivanco said. Tlatlaya is in Mexico state, some 240 km southwest of Mexico City. Mexican media at the time reported that the warehouse was a synthetic drug lab run by the La Familia Michoacana cartel. The military did not address those reports. Some 80,000 people have been killed in drug-related violence in Mexico since 2006.