Guards at the Guantanamo Bay prison fired non-lethal shots to quell prisoner unrest Saturday as they relocated inmates into individual cells, US military officials said.

Officials at the US-run prison met with resistance from some inmates as they moved before dawn to relocate inmates from communal housing into individual cells.

“Some detainees resisted with improvised weapons, and in response, four less-than-lethal rounds were fired,” according to a statement from Robert Durand, a spokesman with Joint Task Force Guantanamo, which runs the prison.

He said there were “no serious injuries to guards or detainees” during the operation aiming “to reestablish proper observation” at the facility.

The shots fired came from two crowd-dispersal rounds about the size of a pea and two rubber bullet rounds known as the M1012 Non-Lethal Point Control Cartridge.

Each crowd-dispersal round contains 18 rubber balls of .32 caliber with “limited ability to penetrate skin and little ability to cause injury,” according to Durand.