Criminal charges have been laid against four inmates for their alleged roles in a riot at the Saskatchewan Penitentiary that resulted in the death of a prisoner.

Upwards of 200 inmates caused extensive damage last December in the medium-security wing of the federal institution in Prince Albert.

Correctional Service Canada said at the time that three inmates were assaulted by the rioters and 43-year-old prisoner Jason Leonard Bird died.

All of the men are charged with participation in a riot.

Three of the inmates are also charged with wearing a mask with intent to commit an indictable offence, while others are facing counts of mischief and obstructing justice by obscuring prison security cameras.

It's not yet clear if more charges will be laid.

All four made a court appearance Wednesday in Prince Albert via video link and are to return to court Oct. 11.

Two of the inmates are still at Saskatchewan Penitentiary.

One has been sent to the maximum-security wing of the Edmonton Institution and another is at the Regional Psychiatric Centre in Saskatoon.

Correctional Service Canada said staff discovered the three injured inmates while securing the ranges in the unit. All three were in serious condition when they were sent to hospital.

Six other inmates suffered non-life-threatening injuries when the penitentiary's emergency response team opened fire with shotguns while storming the prisoners' barricades to end the disturbance.

A representative with the Union of Canadian Correctional Officers said prior to the violence, inmates were dissatisfied with the quality and portion size of food being served to them.

The representative said fires were set, windows were smashed and parts of the institution were flooded during the riot.

The department said it would review the cause of the riot and look at making any necessary changes to its policies and procedures.