Canada's Transportation Safety Board (TSB) said Tuesday that it can't identify the mysterious flying object that nearly collided with a Porter flight descending into Bill Bishop Toronto City Airport last week.

A TSB spokesperson said investigators, who initially believed the flying object may have been a drone, have done as much as they can to figure out what it was. It's unlikely the object was an unmanned aerial vehicle, the TSB said, as it was flying higher and farther out from shore than most drones can go.

Pilots thought the object flying at around 9,000 feet may have been a balloon, but didn't take any chances and took evasive action to dodge it. Two flight attendants suffered minor injuries as the Ottawa-Toronto flight zig-zagged over Lake Ontario near Pickering.

None of the passengers on board were injured.

The TSB spokesperson said the incident will be added to a database, but no formal report will be filed about the incident.