Toronto police performed a controlled detonation of three bombs in an isolated waterfront area on Friday after transporting the devices from the city's east end amid heavy security.

Police used a specialized explosives trailer on Friday to transport the explosive devices down Toronto's Don Valley Parkway to a secure location.
(CBC)

Investigators alleged the devices — described as 35- to 45-centimetre packages with an as yet unidentified explosive — were discovered after a man driving the vehicle was arrested late Thursday night in connection with three letter-bomb incidents earlier this month.

Police took the extraordinary step of closing off a major roadway to transport the bombs and perform the controlled detonation at about 3 p.m. ET. A large plume of smoke rose from the site.

Just after noon ET, a special explosives trailer carrying the devices slowly began travelling southbound on the Don Valley Parkway —  just metres from long-weekend traffic filling the northbound lanes — to the Leslie Street Spit more than seven kilometres away at the edge of Lake Ontario.

Deputy Chief Tony Warr said the extraordinary safety precautions were necessary after bomb technicians determined the bombs could not be defused.

"It's the safest place to do it," he told reporters from the edge of the cordoned area. "We're not able to disassemble them to the point where we can completely take them apart."

Early Friday, the emergency task force sealed off a large perimeter around Overlea Boulevard, Millwood Drive and Don Mills Road, as well as the entire Thorncliffe Park Drive loop, as the bomb disposal units used a pair of remote-controlled robots to move the devices into the trailer.

Investigators also searched a residence on Ashdale Avenue, which was cleared,  police said.

Incidents believed linked

Warr said investigators believe the three earlier incidents are linked to the devices found Friday — "they're similar" — and that the motive appears personal.

Two of the letters were sent to homes in Toronto, while another was sent to a residence in Guelph.

On the evening of Aug. 11, a man in the Victoria Park Avenue-Lawrence Avenue East area sustained injuries after an envelope he received at his home exploded in his hands.

Eight days later, a real estate lawyer found an envelope at his home in the Yonge Street-Sheppard Avenue West area. The package smelled like petroleum, so he notified police and it was safely detonated. Police said it was rigged to explode if opened.

On Aug. 22, a self-employed home renovator found a Canada Post Xpresspost envelope at the rear of his Guelph home, but didn't open it and called police. Media reports said the letter was detonated at the scene and contained enough explosive to take the man's head off had it exploded.

Similar packages mailed to addresses in Toronto and Guelph did not explode, authorities have said.

Adel Arnaout, 37, of Toronto, has been charged with three counts of attempted murder, three counts of intending to cause an explosion, and possession of explosives for an unlawful purpose, police said. He was scheduled to appear Friday in a Toronto court.