 A minor fire at Los Alamos in January 1945 led to a fear that a fire in the plutonium laboratory might contaminate the whole town, and Groves authorized the construction of a new facility for plutonium chemistry and metallurgy, which became known as the DP-site.The hemispheres for the first plutonium pit (or core) were produced and delivered on 2 July 1945.Three more hemispheres followed on 23 July and were delivered three days later.