 Conant informed Manhattan Project director Brigadier General Leslie R. Groves Jr., who in turn assembled a special committee consisting of Lawrence, Compton, Oppenheimer, and McMillan to examine the issue.The committee concluded that any problems could be overcome simply by requiring higher purity.Oppenheimer reviewed his options in early 1943 and gave priority to the gun-type weapon, but he created the E-5 Group at the Los Alamos Laboratory under Seth Neddermeyer to investigate implosion as a hedge against the threat of pre-detonation.