Police are investigating, and one youth was arrested after a late-night assault left one woman with critical injuries in hospital.

James Fargo lives near where the severely injured woman was found late Tuesday night in the area of 93 Street and 103 Avenue, and arrived in time to see emergency crews arrive just before midnight – and at first thought he witnessed the first homicide of 2012.

"There was no rush to hospital," Fargo said. "The ambulance sat there, no lights on, for a half hour,

"Then even when it left the neighbourhood and went out it didn't have [it's] lights on."

Police had few details to release, but called the incident an assault, but confirmed the woman is alive, and in serious condition in hospital.

CTV News has learned a youth was arrested Wednesday at the Edmonton Public Library, and more details will be released as their investigation continues.

With files from David Ewasuk