A prisoner remains in unknown condition in hospital Thursday after he was subdued by a Taser during a struggle outside a holding cell at Edmonton police headquarters Wednesday afternoon.

The officers were getting the large, 34-year-old man ready for a bail hearing at about 4 p.m. when he "snapped," said Sgt. Tony Simioni, president of the Edmonton Police Association.

More than 12 officers responded after an officer-in-distress alarm was sent out.

Simioni described the 10-minute struggle as "massive" and "catastrophic," with TV monitors ripped from the walls, computers destroyed and desks overturned.

"He appeared to be under the influence of some kind of substance," said Simioni. "There was a great deal of effort to try to get and keep this man under control."

At least two officers were hurt in the melee which lasted until one of the officers used a Taser to subdue the man.

The man went into what police are calling a "medical episode," failing to respond to any external stimuli.

Officers provided CPR and mouth-to-mouth resusitation until paramedics arrived, said Simioni.

The man was still breathing when he left the building, he said.

EPS notified the Solicitor General’s office, which subsequently directed EPS to continue with the investigation under the oversight of the Alberta Serious Incident Response Team (ASIRT).

EPS homicide detectives are leading the investigation.

ASIRT investigates incidents or complaints involving the serious injury or death of any person that may have resulted from the actions of a police officer.

Police said the incident was caught on video, which will not be released at this time.