Few month ago in Serbia occurred a interesting phenomenon. Apparently 44 kids felt sick at the same moment, and 14 of them lost conciseness. Authorities still doesn't have any clue what may cause this kind of act, but they are suspecting on sound wave (infra-sound) Did anyone read something about this? Did anyone had similar experience?

Here is the external link, but its in Serbian language.
http://www.telegraf.rs/vesti/1446603-jos-jedna-luda-teorija-djaci-u-sajkasu-se-onesvestili-zbog-zvucnih-talasa

My theory
>experimental drug
>paranormal phenomenon
>mass hysteria caused by someone who created powerful psychic atmosphere
>military testing something