Norway has stopped exporting heavy water because of allegations that foreign nations are using it to manufacture nuclear weapons, Foreign Minster Thorvald Stoltenberg said Wednesday.

Heavy water is vital to the production of plutonium, a key component in nuclear bombs.Stoltenberg, speaking on national radio, said the Labor Party government halted heavy water exports because the sales had "damaged" Norway's image and credibility. He also said the government will investigate past sales to determine whether foreign countries used Norwegian heavy water to help build nuclear bombs.