Toronto police are asking for the public's help in identifying a person who was caught on surveillance video approaching a historic downtown building around the time it was engulfed in flames early Monday.

"We have, as a result of one of the local business owners, obtained CCTV footage of a person of interest," Det. David Love told reporters gathered in front of the burned-out building on Friday afternoon.

It's not clear whether the "person of interest" is a man or woman, Love said. He described the individual as wearing light jeans, a dark jacket with a hood over their head and a cream-coloured backpack.

Love said police would like to speak with the person because he or she was in the area both before and after the fire broke out.

In the video, the person is seen approaching the building by foot from an alleyway at around 1:30 a.m. the night of the fire, Love said. He or she then leaves the area at about 3:50 a.m.

The six-alarm blaze quickly destroyed the historic Empress Hotel near Yonge and Dundas Square early Monday morning. The building had been abandoned months ago, after part of its facade crumbled.

Firefighters were called to the scene at around 4 a.m. that morning. Some 100 firefighters and 32 fire trucks were needed to douse the flames.

Investigators have spoken to the building's owners and they are co-operating with the investigation, Love said.

Investigators who have been sifting through the burned-out rubble at 335 Yonge Street since then suspect arson.

They have not, however, determined whether the person caught on tape had anything to do with sparking the pre-dawn fire.

The building, built in the late 1800s, was designated as an official heritage site last summer. But it has been surrounded by a security fence since April, when a portion of its facade crumbled onto the street.

Since the pre-dawn fire incinerated much of the vacant heritage building's interior structure on Monday, it was deemed unfit for investigators to even enter in their hunt for clues.

Instead, it has been demolished and will be examined piece-by-piece.

While the busy downtown stretch of Yonge Street that passes by the historic site remains closed to traffic between Gerrard and Dundas Streets, the sidewalk on the west side of Yonge has been reopened to pedestrians.

For area stores that have been closed since the inferno Monday, the chance to welcome customers back couldn't come too soon.

"It's definitely affected our sales a lot," the manager at an American Apparel store told CTV Toronto.

But at the nearby Chipotle Mexican Grill, the manager is concerned people won't know they're back in business.

"We're still getting phone calls from customers asking if we're open," Amy Lane told CTV Toronto. "People think we're closed, but we are open."