A number of U.S. military bases in Europe went on heightened alert over the weekend over apparent concerns about possible terrorist activity or targeting of personnel or facilities.

The alert was issued at U.S. European Command headquarters in Stuttgart, Germany. It was a communitywide alert that the force protection threat level was elevated to condition “Charlie” until further notice, according to Stars and Stripes.

The condition Charlie threat level “applies when an incident occurs or intelligence is received indicating some form of terrorist action or targeting against personnel or facilities is likely,” according to the Army’s website.

EUCOM said in a statement Sunday that it is “constantly assessing a variety of factors that play into the safety of the U.S. military community abroad. As part of that effort, we often times take additional steps to ensure the safety of our service members.”