A mail bomb that exploded in a Mexican campus injured two professors, authorities said.
Prosecutor's spokesman Alfredo Albiter says investigators are trying to determine whether the bomb was detonated with a timer or by touch.
There was no indication of the motive.
Mexico's Interior Ministry says the professors suffered second- and third-degree burns. It says they were able to get themselves to a hospital and are listed in stable condition. Their names haven't been released.
Based on reporting by The Associated Press.