Three Haitian prisoners have been killed during a riot put down by UN peacekeepers and Haitian police.
The trouble at Haiti's largest prison broke out after a prisoner stole a guard's weapon in an escape attempt.
The man released other prisoners and they briefly took four other guards, two foreign aid workers and a prison clerk hostage.
UN peacekeepers in Port-au-Prince were called to help end the stand-off at the overcrowded prison.
A national police spokesman told the BBC that the prison was built to accommodate 400 people but was holding 1,500 inmates.
A spokesman for the UN's force in Haiti, known as Minustah, said the prison authorities were unable to bring the riot under control and called for help.
"When they noticed that a riot was forming up inside the prison, they called Minustah for help," Vincenzo Pugliese told the BBC.
"They decided that Minustah should stay outside and reinforce the perimeter of the prison and not go inside. So all the situation inside was handled by the PNH [Haitian police] and the officers of the penitentiary direction administration."
He said between five and seven UN police officers were slightly injured during the riot.
Haiti's over-crowded prisons have seen trouble before.
Following the 12 January earthquake, thousands of prisoners escaped from the country's main prison in Port-au-Prince.
A week later, at least 12 prisoners died and 40 were wounded in an escape attempt from a prison in the city of Les Cayes.