A fire that destroyed 60 townhouses under construction this week west of Toronto was declared to be a $10 million arson, police said.

In a release, Peel Regional Police said they were seeking a suspect seen in a security video as well as a witness who likely would have seen the suspect Monday night in the city of Mississauga.

"Sometime between 8:00 p.m. and 10:30 p.m., the suspect entered the construction site and set the fire," the release said.

The first emergency calls came in around 11 p.m. Monday, and firefighters found several units already fully engulfed, the release said.

The fire was escalated to three-alarm status and it took some 50 firefighters more than two hours to bring it under control, the Toronto Sun reported at the time.

No injuries were reported.

The witness being sought was operating an ice cream vending truck and was in the immediate area of where the security cameras recorded the suspect, who was wearing a hooded, dark jacket and dark pants, police said.