An inmate walking in leg irons and handcuffs is escorted back to a corrections van after being treated at Campbellford Memorial Hospital after a riot at Warkworth Penitentiary overnight Wednesday, July 22, 2009. (Sun Media/Pet Fisher)

BRIGHTON TOWNSHIP -- As many as one-third of the inmates at Warkworth penitentiary have taken control of a portion of the prison – including its infirmary – after an uprising overnight.

"They got into the hospital area and took control," said one emergency services worker standing outside the front gate.

Four inmates were transferred to hospital in nearby Campbellford as correctional workers battled to regain control of the prison.

The four were suffering from suspected narcotics overdoses, according to Ann Anderson, assistant warden, management services.

"The medical centre was breached and we now have correctional officers keeping inmates in the yard to prevent another breach," she said. "There have been no demands from inmates. It started at 9 p.m. last night and there will be an investigation as to why."

The Riot Act Proclamation was read around 5:50 a.m., meaning the institution could use whatever force necessary to gain control of the situation, Anderson said.

Teams from Millhaven, Joyceville and Kingston penitentiaries were called in to help.

"They are burning anything they can get their hands on," a firefighter on scene said, adding he understands the inmates' recreation centre may have been torched.

It was a tense scene overnight as corrections staff, armed in riot gear and firing tear gas, tried to regain control of the prison as firefighter and ambulance stood by.

Fires burned throughout the night inside the walls in a yard area from where you could hear inmates cheering and yelling "let it burn."

The riot squad entered just after 6 a.m.

Warkworth has 579 inmates and 340 staff. No staff have been hurt in the takeover.