The Rocky Flats Plant, a former United States nuclear weapons production facility located about 15 miles (24 km) northwest of Denver, caused radioactive contamination within and outside its boundaries. The contamination primarily resulted from two major plutonium fires in 1957 and 1969 and from wind-blown plutonium that leaked from barrels of radioactive waste. Much lower concentrations of radioactive isotopes were released throughout the operational life of the plant from 1952 to 1992, from smaller accidents and from normal operational releases of plutonium particles too small to be filtered. Prevailing winds from the plant carried airborne contamination south and east, into populated areas northwest of Denver.