The U.S. State Department has sent out a travel alert calling on Americans to be extra vigilant at outdoor festivities and public events in Europe over the year-end holidays. The warning comes just a day after seven people were arrested on charges they were plotting an attack in Strasbourg, France. French Interior Minister Bernard Cazeneuve said the thwarted plot had “been envisaged for a long time on our soil.” While U.S. officials said the travel alert was not connected to any single threat, it does specify fears over the Islamic State terror group waging attacks during the holiday season. “U.S. citizens should also be alert to the possibility that extremist sympathizers or self-radicalized extremists may conduct attacks during this period with little or no warning. Terrorists may employ a wide variety of tactics, using both conventional and nonconventional weapons and targeting both official and private interests,” the alert warns. CNN reports the individuals arrested in France were between 29 and 37 years of age, and investigators believe they were reporting to a handler in Syria linked to ISIS who is still active.