Departing flights were put on hold for more than two hours after a security guard noticed what appeared to be a prohibited item on the screen of an X-ray machine, said Renee Fairweather, spokeswoman for the Canadian Air Transport Security Authority.

Fairweather could not comment on what the item was thought to be, but said prohibited items include sharp objects and liquids.

"The images are left on the screen for some time after the bag goes through. The image was noticed after the bag was gone" said Fairweather.

In order to find the bag, airport security had to recheck all passengers and their carry-on luggage.

The result meant huge delays -- but no prohibited item was discovered.

"The bags were rechecked and nothing was found" said Fairweather.