Several federal prison guards at the maximum security Kent Institution in B.C.’s Fraser Valley are under criminal investigation after an inmate was allegedly brutally assaulted, CBC News has learned.

At least three separate investigations have been launched into the alleged actions of the corrections officers accused of involvement in the attack. And sources tell CBC News that those investigations will also examine a pattern of violent behaviour involving so-called "rogue guards."

The Kent Institution, near Agassiz houses some of Canada's toughest inmates and leads the country in lockdowns, during which prisoners are confined to their cells for weeks at a time.

The prison is “like a powderkeg,” said lawyer John Conroy, who represents an inmate who was a witness to part of the incident.

Conroy said a group of guards were involved in the latest incident.

"He is attacked by one guard, hit several times in the face, goes to the ground, and is then kicked and so on by others who are standing around," Conroy said.

The August assault was allegedly caught on new high-definition surveillance cameras recently installed in Kent.

The incident is now the subject of a criminal investigation by the RCMP, a review by Correctional Services Canada and a probe by the federal government's Correctional Investigator, Howard Sapers.

Guards cited in 2010 report

Sapers filed a scathing report after investigating a 2010 lockdown and search at Kent Institution.

The report heavily criticized the actions of guards and lack of management by staff.

It found that inmates who were compliant and handcuffed were removed from their cells at gunpoint as loaded weapons were pointed at them — a level of force that, “was unwarranted, beyond what was authorized, and dangerous."

Sapers told CBC News some of the systemic and chronic problems at Kent are being addressed.

He said he is currently reviewing 18 use-of-force incidents since April.

"I'm very concerned about the trend in corrections — in federal corrections — right now, and the trend is use-of-force incidents are going up," Sapers said.

The inmate who was allegedly assaulted in August has been transferred to another prison and is not cooperating with the investigations.

With files from the CBC's Eric Rankin