A fourth suspicious device was found at a costume store in Etobicoke Monday night, just hours after the store reopened.

Explosives were found at Amazing Party and Costume on Oxford Street, near the Gardiner Expressway and Islington Avenue over the weekend, resulting in the store being evacuated and shut down for the weekend as a police bomb squad was called in.

The call for the most recent device came in just after 7 p.m. Monday evening, Toronto police said.

The premise was evacuated as the Emergency Task Force was brought in.

Police said the store was open at the time the device was discovered by employees.

It is not clear whether the device had been placed in the store Monday or if it had been there over the weekend, police said.

"This is business terrorism," owner Sean Hamilton told CP24's Farah Nasser earlier on Monday.

Hamilton said he has his suspicions about who may have placed the devices in his store, but so far police have no suspects and haven't established a motive.

He said the incident was frightening for his family and staff.

"They scared myself, my family," Hamilton said. "I have four children who work here."

Employees were given the option to work Monday, he said.

Staff closed the store after the first suspicious device was found Friday, but it reopened later in the day. Two additional devices were found by employees Saturday, forcing the store to close for the rest of the weekend leading up to Halloween.

At least two of the three devices are considered to be explosives.

After the discovery, police set up a command post, closed a stretch of Oxford Street and spent a considerable amount of time scouring the store for any suspicious objects over the weekend.

Building deemed safe

Hamilton said police deemed the building to be safe late Sunday night.

"Police and hundreds of specialized personnel were here combing the store … and they gave me the all clear," Hamilton said.

Hamilton said his store likely lost out on $300,000 in sales because it was closed on some of the busiest days of the year as people bought last-minute Halloween costumes and decorations.

He told CP24 he's holding a sale this week to try to lure customers into his store to make up for the lost business so he can pay his employees and suppliers.

'Act of terrorism'

Meanwhile, Hamilton released the following statement on his store's website:

Many of you have seen or heard the stories in the media regarding the "suspicious packages" that were found in the store and it is, regrettably, true.

We were forced to close the store while the investigation was begun and the specialist agencies have been working to ensure that we are safe to open again.

There are no words to express the gratitude we feel towards our loyal customers, suppliers and neighbours for their support and understanding during this act of terrorism.