They tested the first atomic bomb in a relatively remote location in the wee hours of the morning. That being said there were still many people around the test site. To deal with this, the Manhattan Project security officers dispatched undercover agents to all of the nearby towns. Their job was to listen to any "chatter" that came regarding the tests and to see if any of it was serious. (They also had scientists stationed there with radiation-detecting equipment — they did not know if radiation would be a major concern and whether they would need to evacuate local residents.)

After the test, the project directors released a false press release that claimed it was an ammunition dump exploding. This apparently all did the trick since nobody in the nearby area did any significant poking around into the event.