The animal was locked up at a local jail that normally holds people for public drunkenness and other disturbances after it bit and kicked two men near a ranch in Chiapas state, police said Monday.
Officer Sinar Gomez said the donkey will remain behind bars until its owner agrees to pay the men's medical bills.
"Around here, if someone commits a crime they are jailed," Gomez said - "no matter who they are."
The owner, Mauro Gutierrez, told The Associated Press he would try to reach a friendly arrangement to pay the men's bills, estimated at US$420 (euro270).
The victims said the donkey bit Genaro Vazquez, 63, in the chest on Sunday and then kicked 52-year-old Andres Hernandez as he tried to come to the rescue, fracturing his ankle.
"All of a sudden, the animal was on top of us like it was rabid," Hernandez said.
Police said it took a half-dozen men to control the enraged burro.
Chiapas police have thrown animals in the slammer before, including a bull that devoured corn crops and destroyed two wooden vending stands in March.
In 2006, a dog was locked up for 12 days after biting someone. His owners were fined US$18.
