The development adds a new twist to a probe that has come under fire from international human rights groups and independent investigators.
Two Mexican federal police officers allegedly participated in the disappearance of 43 Ayotzinapa students, the National Human Rights Commission said Thursday, implicating national agents in the 2014 case for the first time, Agence France-Presse reports.
Jose Larrieta Carrasco, a commission official investigating the case, said the authorities should now look into a "new route in the disappearance" of the students.
Prosecutors have already charged municipal police officers in connection with the mass abduction in the southern city of Iguala on September 26-27, 2014.
But the governmental rights commission said it found an eyewitness who saw two federal agents near Iguala's courthouse, where municipal officers had stopped a bus carrying 15 to 20 students.