"La Libre Belgique" has reported about 70-80 Belgians there. We can't be happy with the fact, sure thing!
I strongly doubt they were sent there by our state structures, government or secret services. I guess, those are mainly "men of war" prone to unusual experience and they were just recruited by some Syrian agents or CIA men supportive of the Syrian rebels. Sure thing, those guys upon their arrival back into Belgium are going to pose real security threat! I think you must know about "Syrian syndrome", "live bombs" manipulated by Islamites and just newly born "jihadists".
I just know one such poor guy who was luckily taken into special psycho hospital in time just before he could finish up a self-made bomb and put it into action in some crowdy place so that "to kill infidels". He was recruited in Egypt during his touristy tour to be further sent into Afghanistan. He is now calling all the Europeans by one word only "infidels".
BTW I picked it up somewhere in Inet that Holland authorities have already boosted the degree of alarm over the increase terrorist threat to the level "big threat" fearing the return of the "jihadists" from Syria.