Nobody knew what to expect from the blast of the first atomic bomb. The pre-prepared press releases are pretty bizarre!

William L. Laurence was a newspaper reporter and he was the only reporter brought in to view the Manhattan Project. He was a science journalist at the New York Times and General Groves thought he would therefore be just the man to write the press releases, official statements and newspaper articles concerning the project.

Laurence had to write a series of press releases to cover the Trinity test with stories that were (to say the least) not completely true. The people involved knew that Trinity would make a huge noise and would not go unnoticed, so they had to come up for an excuse - like an exploding ammunition dump, or something similar – to distribute to the surrounding areas

They had no idea how loud the noise would be, so Laurence had to write press releases that would cover every possible scenario. He wrote a series of escalating press releases, depending on how awful the test was. Form A started with “no loss of life or injury” and by the time it got to Form C it read “Among the dead were…” Form D depressingly stated “caused serious damage in some sections of the communities in the area.” It is obvious why he had to write it beforehand – it could have ended up being scenario D, and then he would have been “among the dead”!

(Source)