Thousands of people marched in Mexico City Tuesday to mark 19 months since the disappearance of 43 students in the southern state of Guerrero. The protest came after an international panel of experts released its final report casting doubt on the Mexican government’s account of what happened to the students, and accusing the government of stonewalling and retaliating against investigators. Speaking in Geneva Tuesday, U.N. human rights spokesperson Rupert Colville expressed concern.

Rupert Colville: “We are, however, concerned about the many challenges and obstacles reported by the experts that may have prevented certain lines of inquiries from being further explored, including regarding the roles and responsibilities of the military and other official authorities.”