The man whose party supply store has been the target of recurring bomb scares over the past week says he's resorting to "underground sources" to help find the culprits.

Shawn Hamilton, owner of the Amazing Party and Costume Store, made the comment to reporters on Wednesday.

When asked whether by "underground" he was referring to organized crime, Hamilton replied: "I'm not even going to get into that."

The bomb scares took place over the busy Halloween weekend, forcing the Etobicoke store to close temporarily. Hamilton claims the ordeal has cost him $500,000 in lost sales.

"I am going to come after the people who are doing this," Hamilton said, announcing a $10,000 public reward for the identity of the people responsible for placing seven explosive devices inside his business.

"It is your turn to be terrorized and frightened that you are going to be found by the thousands of hours that the police and the government and the underground and the public are going to be searching for you."

The Toronto police's organized crime unit has joined the investigation at the store, which is located near the Gardiner Expressway and Islington Avenue.

Police had left the area by Wednesday afternoon, but Hamilton said he had not received word that he could re-open.

Hamilton said he has not been contacted by those responsible to explain why explosives were left in his store and demanded that those behind the "business terrorism" come forward.

"If this is a competitor that is doing this for money: stop being so greedy, stop being so lazy," he said. "If this is a personal vendetta against me -- come to me. Don't threaten my business and my employees."

The store owner's lawyer, Calvin Barry, said the fact that the Toronto police's organized crime unit has joined the investigation is "suspicious and doesn't bode well in terms of who'd be doing this."

CTV Toronto's Tamara Cherry pointed out that the intervention of the organized crime unit suggests it was a targeted attack, but not necessarily involving a gang.

Police have said all seven packages found in the store contained explosives, and could have been deadly had they detonated.

"They are active devices; they do have the potential to cause serious harm or death, or serious property damage," Insp. Gerry Cashman told reporters on Tuesday.

Scare began Friday

A bomb squad was called to the business for the first time on Friday after staff found a suspicious package.

Two more packages were found at the location over the weekend – one by a police sniffer dog and another by an officer while searching through the store's inventory. A bomb disposal robot was used to remove them from the scene.

The store re-opened on Monday only to be closed again when a staff member discovered a fourth explosive package. Police say a fifth device was uncovered during their search early Tuesday morning.

The sixth and seventh devices were uncovered Tuesday afternoon, forcing neighbouring businesses to remain closed while police searched the building.

Coun. Mark Grimes said the timing of the bomb scares was unfortunate.

"That this should happen during Halloween when there usually a high traffic of children, parents and customers in general is regrettable and shocking," he said in a statement Tuesday afternoon.

Grimes also noted that the costume store and several nearby businesses have lost revenue as a result of the incidents.