A mail bomb that exploded in a Mexican campus injured two professors, authorities said.

The prosecutor's office for the state of Mexico says a messenger service delivered the package Monday to the cubicle of one of the victims at a campus of Monterrey Technological Institute.

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.

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