It is perfectly possible for emergency codes to be used, in order not to panic the people inside. e.g. A well known large public building in London (used to have?) in the event of (say ) a bomb threat, "Will staff members responsible for administration, report to room 99." This meant the you had to search your area for suspicious ityems and report in if anything found. A perfectly innocuous announcement to all but those in the know, but getting the message to those who needed to act.