Mining of the Suez Canal in 1984 by unknown saboteurs was not effectively countered by sweeping, and ships were damaged. Newer mining armaments technology may include non-metallic, undetectable mines; 'smart' naval mines that move; and systems approaches to land mining, particularly around fixed tactical or strategic installations, that are not possible to sweep (such as time-delay fuses on nylon-canistered devices, or C-B mines). The material remnants of war, particularly mines and unexploded bombs have been left on the territories, most recently in developing countries. These materials seriously impede development and cause injuries and the loss of lives and property. In situations such as in Angola in 1993 where fighting continues intermittently reliefs supplies are cut off. People faced with starvation are obliged to dig up cassava root crops in long-abandoned fields containing unexploded mines.