You sure can!
As per the "Affecting Multiple Targets" section of the SRD, you can either attach an Aspect to the scene (such as setting it On Fire):
The easiest way to do this is to create an advantage on the scene, rather than on a specific target. A Gas-Filled Room has the potential to affect everyone in it, and it’s not too much of a stretch to suggest that the Inspirational Mood in a room could be contagious. In this context, the aspect presents an excuse to call for a skill roll (using the overcome action) from anyone in the scene who attempts to get past it. Generally speaking, it won’t cause damage, but it will make things more difficult for those affected.
… or split your shifts and assign them to individual targets:
Things get more complicated when you want to filter specific targets, rather than just affect a whole zone or scene. When that happens, divide your resulting total up against every target, who all get to defend as per normal. Anyone who fails to defend either takes stress or gains an aspect, depending on what you were trying to do. (Note: If you create an advantage to put an aspect on multiple targets, you do get a free invocation for each one.)