Fire crews battled a 4-alarm blaze in the city's downtown area early Thursday morning.

Crews were called to 301-A George Street in the Jarvis St. and Dundas St. area, at approximately 4:20.

When crews arrived they found the back of the three storey vacant row house building fully engulfed and was moved it up to a 3-alarm fire within 10 minutes of crews receiving the call. It was upgraded to a 4-alarm fire shortly after 6:15.

Adjacent homes were evacuated as a precaution.

No one was inside the house at the time but crews were able to rescue two cats.

The area affected is one of the city's oldest neighbourhoods with houses that were built in the 19th and early 20th century. Most of the homes have been designated as heritage sites by the city.

Heritage experts are looking into the possiblity that the fire may have been a case of demolition by neglect, where homes are abandoned and are allowed to sit vacant and crumble. Area councillor Kristyn Wong-Tam says they have issued several infractions against the property manager and says there will be a meeting on Friday morning to determine what they will do about the remaining homes.

The cause of the fire has not been determine but the fire marshal's office has been notified.