A safety stopper for a receptacle includes a top portion and a sealing ring having an inner bead embraced around a rib at the receptacle opening. The stopper is press fitted into the receptacle. A weakened seam is provided between the top portion and the sealing ring. A slide may be provided in the top of the stopper and is moved outward to enable the stopper to be removed after the seam is broken. The stopper may also include a segment which blocks movement of the slide until the sealing ring is removed.