Tourists have been warned to watch their words after two British friends were refused entry to the United States on security grounds because of a tweetmessage.
Before his trip, Leigh van Bryan wrote he was going to ''destroy America''.
The Department for Homeland Security picked up his messages before his arrival in Los Angeles and sent him and a friend home.
Mr van Bryan says he was simply referring to having a good time.
An organisation representing travel agents says it's a reminder tourists should never do anything that might raise concern or suspicion.