A 21-year-old man and a 17-year-old woman suffered severe head injuries after they were "badly beaten" in downtown Toronto early Monday morning.

Officers were called to Church Street and King Street East around 3:20 a.m. by a man walking his dog. They say the bystander was concerned for the victims' safety.

The pair were found lying on the steps of St. James Cathedral, unconscious and "badly beaten," police said.

Police said at the time they believed the pair were injured at another location and made their way to the church steps where they were found. (Tony Smyth/CBC)

They were taken to St. Michael's Hospital in life-threatening condition. The woman is now is now stable, paramedics said, but the young man's condition remains critical.

Not clear where victims were injured

Investigators are investigating the incident as a possible aggravated assault.

They believe the pair were injured at a secondary location and made their way to the church steps where they were found.

Police are still working to piece together exactly what happened. They say it's unclear how or when the victims were injured.

"We are hopeful we will speak with at least one of them today," spokesperson Const. Caroline de Kloet said.

Officers were canvassing the area on Monday for any security cameras that may have captured the alleged attack.

Anyone who was in the area on Monday until 3:20 a.m. is asked to contact police at 416-808-5100.