Officials said that inmates refused to break up the original fight, and several prisoners jumped in and attacked guards.
The government Tuesday night raised the threat to "critical", its highest level, following an emergency Cabinet session.
The meeting could provide powerful imagery to Catholic voters back in the United States as well as the possibility for conflict between a president and a pope who have not often seen eye-to-eye.
For most students in the area, summer vacation is about to begin as school districts will be getting out early this week.
The Congressional Budget Office planned to release its estimate Wednesday of what impact the GOP's House-passed health care overhaul would have on coverage and premiums.