Hmm, it was not quite a press release, but it's in the Smyth report from August 12, 1945: https://www.osti.gov/opennet/manhattan-project-history/publications/sm

Hmm, it was not quite a press release, but it's in the Smyth report from August 12, 1945: https://www.osti.gov/opennet/manhattan-project-history/publications/smyth_report.pdf https://www.osti.gov/opennet/manhattan-project-history/publi... (search for diffusion).