Where any arms or ammunition in respect of which any offence under this Act has been or is being committed are or is found in any premises, vehicle or other place in the joint occupation or under the joint control of several persons, each of such persons in respect of whom there is reason to believe that he was aware of the existence of the arms or ammunition in the premises, vehicle or other place shall, unless the contrary is proved, be liable for that offence in the same manner as if it has been or is being committed by him alone.