At least two members of staff have been injured during an outbreak of violence at a prison in the US state of Indiana, officials have said.
Trouble spread following a fight between two inmates at New Castle Correctional Facility, Indiana's prisons chief J David Donahue said.
Prisoners set fire to mattresses in the facility yard before calm was restored, Mr Donahue said.
The cause of the violence is being investigated, he said.
Television pictures showed officers in riot gear outside the prison fence and inmates crowding along walkways in the prison grounds.
Media reports said inmates at the medium-security jail were unhappy over the transfer prisoners there from jails in Arizona, where there is a problem with overcrowding.