The official confirmed the threat aboard the flight today to the Associated Press. The official spoke on condition of anonymity because he was not authorised to speak publicly about it.
A British Airways spokeswoman said in a statement the plane landed safely in Montreal today after the captain took the decision to divert the aircraft as a precaution.
The plane had 312 passengers and 17 crew members on board.
The airline is providing hotel rooms for the passengers and will rebook them on other flights as soon as they can.