The police arson squad was investigating the fire that gutted the upscale Westmount home of Ari Ben-Menashe.
Police said Monday that a suspect was seen fleeing the scene just before the fire erupted the previous night.
Ben-Menashe has been tied over the years to different foreign governments including Israel, Zimbabwe and Iran.
He was charged in the United States in 1989 with trying to sell military transport planes to the government of Iran — but he was acquitted.
Ben-Menashe describes himself as a former Israeli intelligence agent and current lobbyist who works for various international clients. He has bristled at media descriptions of him as an arms dealer.
A newspaper report last year about his relationship with Arthur Porter prompted Porter to resign as chairman of Canada's spy watchdog.
Porter resigned after the National Post newspaper reported that the Montreal cancer specialist had forged a business arrangement with Ben-Menashe. The article said they had struck a deal on a $120-million aid-for-development initiative from Russia.
The reported deal would have given African Infrastructure Group, a firm owned by Dr. Porter and his family, the chance to manage infrastructure projects in his native Sierra Leone.
In resigning, Porter said he was aware "that the media portrayal (had) the potential to tarnish'' the credibility of the Security Intelligence Review Committee, prompting him to quit as head of the CSIS agency watchdog. He said, however, he did not let his business interests interfere with review committee responsibilities.