The invention relates to a stopper, provided with an obstructor for a can. Said stopper comprises a cap provided with a central opening and an annular skirt, and an annular shaft extending around the opening, in addition to a capsule which is detachably fixed, by means of a tear element, to a free edge of the shaft opposite the opening. The tear element joining the shaft to the capsule is placed in an entrance area at an angle in the free edge of the shaft. At least one sealing lip is disposed on the inner surface of the shaft, and the cap, skirt and capsule of the stopper are moulded in a single piece without any welding or the addition of another component or detachable part. The invention also relates to a method for the production of said stopper by offset injection in a region which is outside the cap.