Thirty-three pilots across Canada have reported being flashed in the eyes by a laser beam while flying, including at least five incidents near Toronto's Pearson International Airport.

Transport Canada is now investigating the incidents, which date back to 2005 and include at least 12 in Ontario.

"It is certainly a concern for us and we're watching it closely," spokesperson Kirsten Goodnough told CTV.ca, saying she has no explanation for the increasing frequency of incidents.

The pilots have complained about someone on the ground shining a laser at their planes, penetrating the cockpit window and flashing the pilots in the eye. The source of the light is unclear.

Goodnough said some of the incidents around Toronto could have involved the small laser pointers used in boardrooms, but the devices would have to be relatively close to the plane to have a serious effect.

She said the more powerful lasers that may be involved would be those used in surgery rooms or at laser light shows, but those are a lot bigger and require heavy machinery. The devices also require permits from Health Canada.

A laser flashing a pilot's eye can distract and even temporarily blind a pilot. In more serious cases, the laser can cause long-term damage to their retinas.

"We're concerned with any activity that distracts pilots and interferes with the safe operation of an aircraft," Goodnough said.

The greatest concern is for planes approaching a runway and preparing to touch down.

In British Columbia and the U.S., several pilots have been forced to retire because of permanent retinal damage from laser beams, according to the Toronto Star. But Goodnough could not confirm that report.

"We're not aware of any pilots who have suffered damage as a result of these activities," she said.

Finding the lasers

Transport Canada is responsible for ensuring the safe operation of aircrafts, but any criminal investigations are left up to local police forces.

Const. Adam Minnion of Ontario's Peel Regional Police, the force responsible for security around Pearson airport, said anyone who purposely shines a light into a pilot's eyes would face a charge of mischief as a minimum.

However, his force has not laid any charges in connection with any incidents near the Toronto airport.

"We don't have any calls about this, which makes it very difficult to act upon " Minnion told CTV.ca after contacting Peel's airport criminal investigation unit.

He said complaints could have been made in other jurisdictions. Toronto police, however, said they have not received any such reports. Other forces around Toronto did not return phone calls to CTV.ca.

The laser incidents are a cause for concern, Minnion said, but he wouldn't speculate on the nature of the incidents.

The FBI has prosecuted some U.S. residents for purposely shining lights into the eyes of pilots. The agency says there have been hundreds of laser incidents in the U.S. over the last 15 years.