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Nearly half a million dollars has been stolen in an armoured truck robbery in the Montreal suburb of Brossard.

Police say two men wearing Halloween masks attacked two employees of the Garda security firm at a Royal Bank branch in a mall at about 11 p.m.

Longueuil Police spokesman Sylvain Stringer says the thieves hit the guards with pepper spray before making off with $431,000.

Stringer says police will be checking security camera footage to learn more about the robbery, such as the kind of vehicle the robbers used to flee.