Police and fire officials are investigating a suspected arson attack on one of Toronto's best-known jewelry shops.

A crudely made incendiary device was thrown through the front window of Harold the Jewellery Buyer's store early Monday morning.

Police and fire crews were called to the scene at 2788 Bathurst St., south of Lawrence Avenue West, about 2:30 a.m. The fire was quickly doused but the store suffered extensive smoke damage.

Although it will be up to the Ontario Fire Marshal's Office to make the final determination, owner Harold Gerstel says he has no doubt it was a deliberately set.

"When you're a leader in the industry, there's always people trying to pull you down," Gerstel told CBC News. "This was meant as an intimidation."

One of the onlookers early Monday morning was a former store employee, Maria Konstan, 71, who was charged earlier this year in an alleged plot to kill Jack Berkovits, the owner of a rival jewelry store, Omni Jewelcrafters.

Gerstel, the owner of the fire-damaged store, has not been charged in the alleged plot and said Monday he intends to reopen his business as soon as possible.

Television commercials advertising "cash for gold" at Harold the Jewellery Buyer's are a constant on some Toronto television stations.