Toronto police are now investigating a two-alarm fire that tore through two houses in Leslieville this week as an arson, and are seeking the public's help in locating a suspect.

The fire, which began in the early hours of Tuesday morning, began in one house under renovation and spread quickly to the semi-detached house next door.

No injuries were reported as a result of the blaze, but a Toronto Fire captain estimated that the damage to the properties was in excess of $500,000.

The fire began in a house under renovation on Booth Avenue and quickly spread next door. (Tony Smyth/CBC)

Police are now seeking a man who was seen in the area at about 3:35 a.m., close to when the fire began, as part of their investigation.

He is described as being in his 30s, with a thin build and a black scruffy beard. When spotted on Tuesday, he was wearing a dark jacket and pants, a baseball cap, and white high-top running shoes.

Anyone with any information is asked to get in touch with police at 416 808 5500, or contact Crime Stoppers at 416 222 8477.